AVideo has Stored Cross-Site Scripting via Markdown Comment Injection

Vulnerability Type

Stored Cross-Site Scripting (XSS) — CWE-79.

Affected Product/Versions

AVideo 18.0.

Root Cause Summary

AVideo allows Markdown in video comments and uses Parsedown (v1.7.4) without Safe Mode enabled. Markdown links are not sufficiently sanitized, allowing javascript: URIs to be rendered as clickable links.

Impact Summary

An authenticated low-privilege attacker can post a malicious comment that injects persistent JavaScript. When another user clicks the link, the attacker can perform actions such as session hijacking, privilege escalation (including admin takeover), and data exfiltration.

Resolution/Fix

The issue was confirmed and fixed in the master branch. An official release will be published soon.

Workarounds

Until the release is available, validate and block unsafe URI schemes (e.g., javascript:) before rendering Markdown, and enable Parsedown Safe Mode.

Credits/Acknowledgement

Reported by Arkadiusz Marta (https://github.com/arkmarta/).