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GHSA-4MF4-73J6-MVRW

Vulnerability from github – Published: 2026-09-16 21:50 – Updated: 2026-09-16 21:50
VLAI
Summary
djust is vulnerable to stored/reflected XSS via javascript: URLs in built-in component template tags
Details

Impact

Many djust built-in component template tags (djust.components.templatetags.*) render a developer/user-supplied URL into an href / action attribute, HTML-escaping it with conditional_escape but never validating the URL scheme. HTML escaping prevents attribute breakout but does not neutralize a javascript: URI (which needs no escapable characters), so a URL value of javascript:alert(document.cookie) lands verbatim in <a href="javascript:alert(document.cookie)"> and executes in the victim's session on click.

Affected sinks (executing href/action contexts; not exhaustive): breadcrumb (djust_components.py:1535; _advanced.py:1999,2022), dj_nav link/dropdown/brand (djust_components.py:5632,5779,5807,5830), citation URL (:6936), cookie-consent privacy link (:8240), error-page action (_advanced.py:1728), form action (_forms.py:1239). <img src> sinks are lower risk (javascript: does not execute via img src). No scheme validation exists anywhere in the component tags; a docstring at djust_components.py:781 even acknowledges the javascript: risk without mitigating it.

Severity Medium: XSS in the victim's authenticated session whenever an app renders one of these components with a URL sourced from user-controllable data; for href requires a click, worst case is the stored variant (URL persisted from one user, rendered to another). Conditional on developer usage, hence Medium rather than High.

Reproduced: breadcrumb(items=[{"label":"Home","url":"javascript:alert(document.cookie)"}]) emits <a ... href="javascript:alert(document.cookie)">Home</a>; JaVaScRiPt: case variant also passes; https:// URLs are preserved.

Patches

Add a safe_url() helper that neutralizes non-allowlisted schemes (javascript:, vbscript:, data:) to # while preserving http/https/mailto/tel/relative/anchor URLs, and route every href/action/formaction/xlink:href sink through it (then HTML-escape). Add a regression + an audit_ast/system-check rule flagging un-routed URL-attribute interpolation.

Workarounds

Do not pass user-controllable URLs to the affected built-in component tags; pre-validate URL schemes in application code before binding them to component arguments.

References

Reproducer + finding writeup retained privately by the maintainer.

Show details on source website

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "djust"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.0.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61597"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-16T21:50:53Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\nMany djust built-in component template tags (`djust.components.templatetags.*`) render a developer/user-supplied URL into an `href` / `action` attribute, HTML-escaping it with `conditional_escape` but **never validating the URL scheme**. HTML escaping prevents attribute breakout but does not neutralize a `javascript:` URI (which needs no escapable characters), so a URL value of `javascript:alert(document.cookie)` lands verbatim in `\u003ca href=\"javascript:alert(document.cookie)\"\u003e` and executes in the victim\u0027s session on click.\n\nAffected sinks (executing href/action contexts; not exhaustive): breadcrumb (`djust_components.py:1535`; `_advanced.py:1999,2022`), `dj_nav` link/dropdown/brand (`djust_components.py:5632,5779,5807,5830`), citation URL (`:6936`), cookie-consent privacy link (`:8240`), error-page action (`_advanced.py:1728`), form `action` (`_forms.py:1239`). `\u003cimg src\u003e` sinks are lower risk (javascript: does not execute via img src). No scheme validation exists anywhere in the component tags; a docstring at `djust_components.py:781` even acknowledges the `javascript:` risk without mitigating it.\n\n**Severity Medium:** XSS in the victim\u0027s authenticated session whenever an app renders one of these components with a URL sourced from user-controllable data; for `href` requires a click, worst case is the stored variant (URL persisted from one user, rendered to another). Conditional on developer usage, hence Medium rather than High.\n\nReproduced: `breadcrumb(items=[{\"label\":\"Home\",\"url\":\"javascript:alert(document.cookie)\"}])` emits `\u003ca ... href=\"javascript:alert(document.cookie)\"\u003eHome\u003c/a\u003e`; `JaVaScRiPt:` case variant also passes; `https://` URLs are preserved.\n\n### Patches\nAdd a `safe_url()` helper that neutralizes non-allowlisted schemes (`javascript:`, `vbscript:`, `data:`) to `#` while preserving http/https/mailto/tel/relative/anchor URLs, and route every href/action/formaction/xlink:href sink through it (then HTML-escape). Add a regression + an audit_ast/system-check rule flagging un-routed URL-attribute interpolation.\n\n### Workarounds\nDo not pass user-controllable URLs to the affected built-in component tags; pre-validate URL schemes in application code before binding them to component arguments.\n\n### References\nReproducer + finding writeup retained privately by the maintainer.",
  "id": "GHSA-4mf4-73j6-mvrw",
  "modified": "2026-09-16T21:50:53Z",
  "published": "2026-09-16T21:50:53Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/djust-org/djust/security/advisories/GHSA-4mf4-73j6-mvrw"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/djust-org/djust"
    },
    {
      "type": "WEB",
      "url": "https://github.com/djust-org/djust/releases/tag/v1.0.7"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "djust is vulnerable to stored/reflected XSS via javascript: URLs in built-in component template tags"
}



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