cve/2021/CVE-2021-38503.md

### [CVE-2021-38503](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-38503)
![](https://img.shields.io/static/v1?label=Product&message=Firefox%20ESR&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=Firefox&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=Thunderbird&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2091.3%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2094%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=iframe%20sandbox%20rules%20did%20not%20apply%20to%20XSLT%20stylesheets&color=brighgreen)

### Description

The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass restrictions such as executing scripts or navigating the top-level frame. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

### POC

#### Reference
- https://bugzilla.mozilla.org/show_bug.cgi?id=1729517

#### Github
- https://github.com/ARPSyndicate/cvemon