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Medium · 5.4 CVE-2026-33500 EUVD-2026-20065GHSA-72h5-39r7-r26j

AVideo Vulnerable to Stored XSS via Markdown `javascript:` URI Bypasses ParsedownSafeWithLinks Sanitization

Published Mar 23, 2026 · Updated Mar 24, 2026 · Assigned by GitHub_M

Description

WWBN AVideo is an open source video platform. In versions up to and including 26.0, the fix for CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introduced a custom `ParsedownSafeWithLinks` class that sanitizes raw HTML `<a>` and `<img>` tags in comments, but explicitly disables Parsedown's `safeMode`. This creates a bypass: markdown link syntax `[text](javascript:alert(1))` is processed by Parsedown's `inlineLink()` method, which does not go through the custom `sanitizeATag()` sanitization (that only handles raw HTML tags). With `safeMode` disabled, Parsedown's built-in `javascript:` URI filtering (`sanitiseElement()`/`filterUnsafeUrlInAttribute()`) is also inactive. An attacker can inject stored XSS via comment markdown links. Commit 3ae02fa240939dbefc5949d64f05790fd25d728d contains a patch.

Affected products

VendorProductAffectedFixed
WWBN AVideo <= 26.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
Packagist wwbn/avideo <= 26.0 — GHSA-72h5-39r7-r26j

References