CWE-79
AllowedImproper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Abstraction: Base · Status: Stable
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
67272 vulnerabilities reference this CWE, most recent first.
GHSA-4P5H-FXJC-527W
Vulnerability from github – Published: 2026-03-16 15:30 – Updated: 2026-03-16 15:30A vulnerability was determined in UEditor up to 1.4.3.2. This issue affects some unknown processing of the file php/controller.php?action=uploadimage of the component JSONP Callback Handler. This manipulation of the argument callback causes cross site scripting. The attack can be initiated remotely. The exploit has been publicly disclosed and may be utilized. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.
{
"affected": [],
"aliases": [
"CVE-2026-4186"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-16T14:19:59Z",
"severity": "MODERATE"
},
"details": "A vulnerability was determined in UEditor up to 1.4.3.2. This issue affects some unknown processing of the file php/controller.php?action=uploadimage of the component JSONP Callback Handler. This manipulation of the argument callback causes cross site scripting. The attack can be initiated remotely. The exploit has been publicly disclosed and may be utilized. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.",
"id": "GHSA-4p5h-fxjc-527w",
"modified": "2026-03-16T15:30:45Z",
"published": "2026-03-16T15:30:45Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4186"
},
{
"type": "WEB",
"url": "https://magnificent-dill-351.notion.site/JSONP-Injection-in-ueditor-1-4-3-2-317c693918ed80cbb96dc8e1a9f0e8b2"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.351092"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.351092"
},
{
"type": "WEB",
"url": "https://vuldb.com/?submit.769842"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-4P5P-HC8F-Q6M8
Vulnerability from github – Published: 2024-08-02 00:31 – Updated: 2024-08-02 00:31Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in WPWeb Elite WooCommerce PDF Vouchers allows Reflected XSS.This issue affects WooCommerce PDF Vouchers: from n/a before 4.9.5.
{
"affected": [],
"aliases": [
"CVE-2024-39652"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-08-01T22:15:26Z",
"severity": "HIGH"
},
"details": "Improper Neutralization of Input During Web Page Generation (XSS or \u0027Cross-site Scripting\u0027) vulnerability in WPWeb Elite WooCommerce PDF Vouchers allows Reflected XSS.This issue affects WooCommerce PDF Vouchers: from n/a before 4.9.5.",
"id": "GHSA-4p5p-hc8f-q6m8",
"modified": "2024-08-02T00:31:25Z",
"published": "2024-08-02T00:31:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-39652"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/vulnerability/woocommerce-pdf-vouchers/wordpress-woocommerce-pdf-vouchers-plugin-4-9-5-reflected-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-4P5Q-8W47-W97R
Vulnerability from github – Published: 2023-08-22 21:30 – Updated: 2024-10-29 21:30Multiple vulnerabilities in the web-based management interface of EdgeConnect SD-WAN Orchestrator could allow an authenticated remote attacker to conduct SQL injection attacks against the EdgeConnect SD-WAN Orchestrator instance. An attacker could exploit these vulnerabilities to obtain and modify sensitive information in the underlying database potentially leading to the exposure and corruption of sensitive data controlled by the EdgeConnect SD-WAN Orchestrator host.
{
"affected": [],
"aliases": [
"CVE-2023-37439"
],
"database_specific": {
"cwe_ids": [
"CWE-79",
"CWE-922"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-08-22T19:16:38Z",
"severity": "MODERATE"
},
"details": "Multiple vulnerabilities in the web-based management\u00a0interface of EdgeConnect SD-WAN Orchestrator could allow\u00a0an authenticated remote attacker to conduct SQL injection\u00a0attacks against the EdgeConnect SD-WAN Orchestrator\u00a0instance. An attacker could exploit these vulnerabilities to\n\u00a0 \u00a0 obtain and modify sensitive information in the underlying\u00a0database potentially leading to the exposure and corruption\u00a0of sensitive data controlled by the EdgeConnect SD-WAN\u00a0Orchestrator host.\n\n",
"id": "GHSA-4p5q-8w47-w97r",
"modified": "2024-10-29T21:30:42Z",
"published": "2023-08-22T21:30:27Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-37439"
},
{
"type": "WEB",
"url": "https://www.arubanetworks.com/assets/alert/ARUBA-PSA-2023-012.txt"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-4P5X-52QW-GRGG
Vulnerability from github – Published: 2022-05-24 19:09 – Updated: 2022-05-24 19:09Stored XSS can execute as administrator in quarantined email detail view in Sophos UTM before version 9.706.
{
"affected": [],
"aliases": [
"CVE-2021-25273"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-07-29T20:15:00Z",
"severity": "MODERATE"
},
"details": "Stored XSS can execute as administrator in quarantined email detail view in Sophos UTM before version 9.706.",
"id": "GHSA-4p5x-52qw-grgg",
"modified": "2022-05-24T19:09:18Z",
"published": "2022-05-24T19:09:18Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-25273"
},
{
"type": "WEB",
"url": "https://community.sophos.com/utm-firewall/b/blog/posts/utm-up2date-9-706-released"
},
{
"type": "WEB",
"url": "http://seclists.org/fulldisclosure/2021/Dec/3"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-4P64-3PJ4-G3CP
Vulnerability from github – Published: 2022-05-02 00:11 – Updated: 2022-05-02 00:11Cross-site scripting (XSS) vulnerability in Shindig-Integrator 5.x, a module for Drupal, allows remote authenticated users to inject arbitrary web script or HTML via unspecified vectors in generated pages.
{
"affected": [],
"aliases": [
"CVE-2008-4596"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2008-10-17T21:29:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in Shindig-Integrator 5.x, a module for Drupal, allows remote authenticated users to inject arbitrary web script or HTML via unspecified vectors in generated pages.",
"id": "GHSA-4p64-3pj4-g3cp",
"modified": "2022-05-02T00:11:42Z",
"published": "2022-05-02T00:11:42Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2008-4596"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/45925"
},
{
"type": "WEB",
"url": "http://drupal.org/node/321758"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/32285"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-4P64-HXGR-8P2M
Vulnerability from github – Published: 2025-04-28 06:30 – Updated: 2025-04-28 18:30The WordPress Tag, Category, and Taxonomy Manager WordPress plugin before 3.30.0 does not sanitise and escape some of its Widgets settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
{
"affected": [],
"aliases": [
"CVE-2025-0627"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-28T06:15:17Z",
"severity": "LOW"
},
"details": "The WordPress Tag, Category, and Taxonomy Manager WordPress plugin before 3.30.0 does not sanitise and escape some of its Widgets settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).",
"id": "GHSA-4p64-hxgr-8p2m",
"modified": "2025-04-28T18:30:54Z",
"published": "2025-04-28T06:30:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-0627"
},
{
"type": "WEB",
"url": "https://wpscan.com/vulnerability/30fbe3c5-f190-48e8-a6bb-e8d78e001e7f"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-4P64-MJ95-V5FC
Vulnerability from github – Published: 2025-06-06 15:30 – Updated: 2026-04-01 18:35Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in impleCode Product Catalog Simple allows Stored XSS. This issue affects Product Catalog Simple: from n/a through 1.8.1.
{
"affected": [],
"aliases": [
"CVE-2025-49305"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-06-06T13:15:46Z",
"severity": "MODERATE"
},
"details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in impleCode Product Catalog Simple allows Stored XSS. This issue affects Product Catalog Simple: from n/a through 1.8.1.",
"id": "GHSA-4p64-mj95-v5fc",
"modified": "2026-04-01T18:35:22Z",
"published": "2025-06-06T15:30:50Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-49305"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/wordpress/plugin/post-type-x/vulnerability/wordpress-product-catalog-simple-1-8-1-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-4P64-MR2W-44CV
Vulnerability from github – Published: 2024-03-17 18:30 – Updated: 2026-04-28 21:34Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in I Thirteen Web Solution Email Subscription Popup allows Stored XSS.This issue affects Email Subscription Popup: from n/a through 1.2.20.
{
"affected": [],
"aliases": [
"CVE-2024-27960"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-03-17T17:15:07Z",
"severity": "HIGH"
},
"details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in I Thirteen Web Solution Email Subscription Popup allows Stored XSS.This issue affects Email Subscription Popup: from n/a through 1.2.20.",
"id": "GHSA-4p64-mr2w-44cv",
"modified": "2026-04-28T21:34:06Z",
"published": "2024-03-17T18:30:49Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-27960"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/vulnerability/email-subscribe/wordpress-email-subscription-popup-plugin-1-2-20-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L",
"type": "CVSS_V3"
}
]
}
GHSA-4P64-V8F5-R2GX
Vulnerability from github – Published: 2026-04-14 20:05 – Updated: 2026-04-14 20:05Summary
justhtml 1.16.0 fixes multiple security issues in sanitization, serialization, and programmatic DOM handling.
Most of these issues affected one of these advanced paths rather than ordinary parsed HTML with the default safe settings:
- programmatic DOM input to
sanitize()orsanitize_dom() - reused or mutated sanitization policy objects
- custom policies that preserve foreign namespaces such as SVG or MathML
Affected versions
justhtml<= 1.15.0
Fixed version
justhtml1.16.0released on April 12, 2026
Impact
Policy reuse and mutation
Nested mutation of sanitization policy internals could weaken later sanitization by leaving stale compiled sanitizers active, or by mutating exported default policy internals process-wide.
In-memory sanitization gaps
Programmatic DOM sanitization could miss dangerous mixed-case tag names such as ScRiPt or StYlE, and custom drop_content_tags values such as {"SCRIPT"} could silently fail to drop dangerous subtrees.
Serialization injection
Crafted programmatic doctype names could serialize into active markup before the document body.
Foreign-namespace policy bypasses
Custom policies that preserve SVG or MathML could allow active SVG features to survive sanitization, including:
- animation elements such as
<set>and<animate>that mutate already-sanitized attributes after sanitization - presentation attributes such as
fill,clip-path,mask,marker-start, andcursorcontaining externalurl(...)references - programmatic DOM trees that claim
namespace="html"but serialize as<svg>or<math>, bypassing foreign-content checks
Rawtext hardening gap
Mixed-case programmatic style or script nodes could bypass rawtext hardening and preserve active stylesheet content such as remote @import rules.
Default configuration
Most of these issues did not affect the normal JustHTML(..., sanitize=True) path for ordinary parsed HTML.
The main exceptions were policy-mutation issues, which could weaken later sanitization if code mutated nested state on reused policy objects or exported defaults.
Recommended action
Upgrade to justhtml 1.16.0.
If you cannot upgrade immediately:
- do not mutate
DEFAULT_POLICY,DEFAULT_DOCUMENT_POLICY, or nested policy internals - avoid reusing policy objects after mutating nested state
- avoid preserving SVG or MathML for untrusted input
- avoid preserving
styleorscriptin custom policies for untrusted input - avoid serializing untrusted programmatic doctypes or DOM trees
Credit
Discovered during an internal security review of justhtml.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.15.0"
},
"package": {
"ecosystem": "PyPI",
"name": "justhtml"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.16.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-178",
"CWE-436",
"CWE-471",
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-04-14T20:05:10Z",
"nvd_published_at": null,
"severity": "LOW"
},
"details": "## Summary\n\n`justhtml` `1.16.0` fixes multiple security issues in sanitization, serialization, and programmatic DOM handling.\n\nMost of these issues affected one of these advanced paths rather than ordinary parsed HTML with the default safe settings:\n\n- programmatic DOM input to `sanitize()` or `sanitize_dom()`\n- reused or mutated sanitization policy objects\n- custom policies that preserve foreign namespaces such as SVG or MathML\n\n## Affected versions\n\n- `justhtml` `\u003c= 1.15.0`\n\n## Fixed version\n\n- `justhtml` `1.16.0` released on April 12, 2026\n\n## Impact\n\n### Policy reuse and mutation\nNested mutation of sanitization policy internals could weaken later sanitization by leaving stale compiled sanitizers active, or by mutating exported default policy internals process-wide.\n\n### In-memory sanitization gaps\nProgrammatic DOM sanitization could miss dangerous mixed-case tag names such as `ScRiPt` or `StYlE`, and custom `drop_content_tags` values such as `{\"SCRIPT\"}` could silently fail to drop dangerous subtrees.\n\n### Serialization injection\nCrafted programmatic doctype names could serialize into active markup before the document body.\n\n### Foreign-namespace policy bypasses\nCustom policies that preserve SVG or MathML could allow active SVG features to survive sanitization, including:\n\n- animation elements such as `\u003cset\u003e` and `\u003canimate\u003e` that mutate already-sanitized attributes after sanitization\n- presentation attributes such as `fill`, `clip-path`, `mask`, `marker-start`, and `cursor` containing external `url(...)` references\n- programmatic DOM trees that claim `namespace=\"html\"` but serialize as `\u003csvg\u003e` or `\u003cmath\u003e`, bypassing foreign-content checks\n\n### Rawtext hardening gap\nMixed-case programmatic `style` or `script` nodes could bypass rawtext hardening and preserve active stylesheet content such as remote `@import` rules.\n\n## Default configuration\n\nMost of these issues did **not** affect the normal `JustHTML(..., sanitize=True)` path for ordinary parsed HTML.\n\nThe main exceptions were policy-mutation issues, which could weaken later sanitization if code mutated nested state on reused policy objects or exported defaults.\n\n## Recommended action\n\nUpgrade to `justhtml` `1.16.0`.\n\nIf you cannot upgrade immediately:\n\n- do not mutate `DEFAULT_POLICY`, `DEFAULT_DOCUMENT_POLICY`, or nested policy internals\n- avoid reusing policy objects after mutating nested state\n- avoid preserving SVG or MathML for untrusted input\n- avoid preserving `style` or `script` in custom policies for untrusted input\n- avoid serializing untrusted programmatic doctypes or DOM trees\n\n## Credit\n\nDiscovered during an internal security review of `justhtml`.",
"id": "GHSA-4p64-v8f5-r2gx",
"modified": "2026-04-14T20:05:10Z",
"published": "2026-04-14T20:05:10Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-4p64-v8f5-r2gx"
},
{
"type": "PACKAGE",
"url": "https://github.com/EmilStenstrom/justhtml"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U",
"type": "CVSS_V4"
}
],
"summary": "Multiple security fixes in justhtml"
}
GHSA-4P72-HVVM-VVPJ
Vulnerability from github – Published: 2025-11-21 15:31 – Updated: 2026-01-20 15:31Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in hupe13 Extensions for Leaflet Map extensions-leaflet-map allows DOM-Based XSS.This issue affects Extensions for Leaflet Map: from n/a through <= 4.8.
{
"affected": [],
"aliases": [
"CVE-2025-66093"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-11-21T13:15:50Z",
"severity": "MODERATE"
},
"details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in hupe13 Extensions for Leaflet Map extensions-leaflet-map allows DOM-Based XSS.This issue affects Extensions for Leaflet Map: from n/a through \u003c= 4.8.",
"id": "GHSA-4p72-hvvm-vvpj",
"modified": "2026-01-20T15:31:56Z",
"published": "2025-11-21T15:31:27Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-66093"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/Wordpress/Plugin/extensions-leaflet-map/vulnerability/wordpress-extensions-for-leaflet-map-plugin-4-8-cross-site-scripting-xss-vulnerability?_s_id=cve"
},
{
"type": "WEB",
"url": "https://vdp.patchstack.com/database/Wordpress/Plugin/extensions-leaflet-map/vulnerability/wordpress-extensions-for-leaflet-map-plugin-4-8-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L",
"type": "CVSS_V3"
}
]
}
Mitigation MIT-4
Strategy: Libraries or Frameworks
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
- Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
Mitigation
- Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.
- For any data that will be output to another web page, especially any data that was received from external inputs, use the appropriate encoding on all non-alphanumeric characters.
- Parts of the same output document may require different encodings, which will vary depending on whether the output is in the:
- etc. Note that HTML Entity Encoding is only appropriate for the HTML body.
- Consult the XSS Prevention Cheat Sheet [REF-724] for more details on the types of encoding and escaping that are needed.
- HTML body
- Element attributes (such as src="XYZ")
- URIs
- JavaScript sections
- Cascading Style Sheets and style property
Mitigation MIT-6
Strategy: Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
Mitigation MIT-15
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Mitigation MIT-27
Strategy: Parameterization
If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.
Mitigation MIT-30.1
Strategy: Output Encoding
- Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
- The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.
Mitigation MIT-43
With Struts, write all data from form beans with the bean's filter attribute set to true.
Mitigation MIT-31
Strategy: Attack Surface Reduction
To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XmlHttpRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.
Mitigation MIT-5
Strategy: Input Validation
- Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- When dynamically constructing web pages, use stringent allowlists that limit the character set based on the expected value of the parameter in the request. All input should be validated and cleansed, not just parameters that the user is supposed to specify, but all data in the request, including hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. It is common to see data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended.
- Note that proper output encoding, escaping, and quoting is the most effective solution for preventing XSS, although input validation may provide some defense-in-depth. This is because it effectively limits what will appear in output. Input validation will not always prevent XSS, especially if you are required to support free-form text fields that could contain arbitrary characters. For example, in a chat application, the heart emoticon ("<3") would likely pass the validation step, since it is commonly used. However, it cannot be directly inserted into the web page because it contains the "<" character, which would need to be escaped or otherwise handled. In this case, stripping the "<" might reduce the risk of XSS, but it would produce incorrect behavior because the emoticon would not be recorded. This might seem to be a minor inconvenience, but it would be more important in a mathematical forum that wants to represent inequalities.
- Even if you make a mistake in your validation (such as forgetting one out of 100 input fields), appropriate encoding is still likely to protect you from injection-based attacks. As long as it is not done in isolation, input validation is still a useful technique, since it may significantly reduce your attack surface, allow you to detect some attacks, and provide other security benefits that proper encoding does not address.
- Ensure that you perform input validation at well-defined interfaces within the application. This will help protect the application even if a component is reused or moved elsewhere.
Mitigation MIT-21
Strategy: Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Mitigation MIT-29
Strategy: Firewall
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Mitigation MIT-16
Strategy: Environment Hardening
When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
CAPEC-209: XSS Using MIME Type Mismatch
An adversary creates a file with scripting content but where the specified MIME type of the file is such that scripting is not expected. The adversary tricks the victim into accessing a URL that responds with the script file. Some browsers will detect that the specified MIME type of the file does not match the actual type of its content and will automatically switch to using an interpreter for the real content type. If the browser does not invoke script filters before doing this, the adversary's script may run on the target unsanitized, possibly revealing the victim's cookies or executing arbitrary script in their browser.
CAPEC-588: DOM-Based XSS
This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is inserted into the client-side HTML being parsed by a web browser. Content served by a vulnerable web application includes script code used to manipulate the Document Object Model (DOM). This script code either does not properly validate input, or does not perform proper output encoding, thus creating an opportunity for an adversary to inject a malicious script launch a XSS attack. A key distinction between other XSS attacks and DOM-based attacks is that in other XSS attacks, the malicious script runs when the vulnerable web page is initially loaded, while a DOM-based attack executes sometime after the page loads. Another distinction of DOM-based attacks is that in some cases, the malicious script is never sent to the vulnerable web server at all. An attack like this is guaranteed to bypass any server-side filtering attempts to protect users.
CAPEC-591: Reflected XSS
This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is "reflected" off a vulnerable web application and then executed by a victim's browser. The process starts with an adversary delivering a malicious script to a victim and convincing the victim to send the script to the vulnerable web application.
CAPEC-592: Stored XSS
An adversary utilizes a form of Cross-site Scripting (XSS) where a malicious script is persistently "stored" within the data storage of a vulnerable web application as valid input.
CAPEC-63: Cross-Site Scripting (XSS)
An adversary embeds malicious scripts in content that will be served to web browsers. The goal of the attack is for the target software, the client-side browser, to execute the script with the users' privilege level. An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute code and scripts. Web browsers, for example, have some simple security controls in place, but if a remote attacker is allowed to execute scripts (through injecting them in to user-generated content like bulletin boards) then these controls may be bypassed. Further, these attacks are very difficult for an end user to detect.
CAPEC-85: AJAX Footprinting
This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.