GHSA-fg89-g389-p346

Summary

In Bagisto v2.3.7, the TinyMCE image upload functionality allows an attacker with sufficient privileges (e.g. admin) to upload a crafted SVG file containing embedded JavaScript. When viewed, the malicious code executes in the context of the admin/user’s browser.

Details

The underlying problem is that SVG is XML/markup, so when it is uploaded and then directly rendered or embedded, script or event handlers within are allowed to run unless sanitized. In Bagisto, the integration of TinyMCE’s image upload (or media manager) may accept SVG files without sanitizing or rejecting unsafe content. When the SVG is later included (inline or via object/embed) in content displayed in admin or UI, the browser may execute the script portion of the SVG. The application might not validate the file content (i.e. inspect the SVG XML) or strip <script>, onload, onclick, foreignObject, xlink:href injection, objects/embed tags, etc.

PoC

Navigate to any forms with TinyMCE editor. Attempt to upload a SVG file with embedded JavaScript. <img width="1580" height="795" alt="image" src="https://github.com/user-attachments/assets/17df21a4-bfcd-4c51-a963-68f68241fd2e" /> JavaScript was triggered. <img width="1402" height="409" alt="image" src="https://github.com/user-attachments/assets/d0e326c3-6f23-449d-8f90-1e1032818d80" />

Impact

Malicious script is stored in SVG file and executed when the content is viewed. An attacker (with upload privilege) can target other admin users or editors who view the content, enabling session hijacking, unauthorized actions, or privilege escalation.