Grav is a content management system (CMS). Prior to version 1.7.43, users who may write a page may use the `frontmatter` feature due to insufficient permission validation and inadequate file name validation. This may lead to remote code execution. Version 1.7.43 fixes this issue.

Affected: Packagist: getgrav/grav

### Summary - Due to insufficient permission verification, user who can write a page use frontmatter feature. - Inadequate File Name Validation

### Details 1. Insufficient Permission Verification

In Grav CMS, "[Frontmatter](https://learn.getgrav.org/17/content/headers)" refers to the metadata block located at the top of a Markdown file. Frontmatter serves the purpose of providing additional information about a specific page or post. In this feature, only administrators are granted access, while regular users who can create pages are not. However, if a regular user adds the data[_json][header][form] parameter to the POST Body while creating a page, they can use Frontmatter. The demonstration of this vulnerability is provided in video format. [Video Link](https://www.youtube.com/watch?v=EU1QA0idoWE)

2. Inadequate File Name Validation

To create a Contact Form, Frontmatter and markdown can be written as follows: [Contact Form Example](https://learn.getgrav.org/17/forms/forms/example-form) [Form Action Save Option](https://learn.getgrav.org/17/forms/forms/reference-form-actions#save) When an external user submits the Contact Form after filling it out, the data is stored in the user/data folder. The filename under which the data is stored corresponds to the value specified in the filename attribute of the process property. For instance, if the filename attribute has a value of "feedback.txt," a feedback.txt file is created in the user/data/contact folder. This file contains th…