CVE-2026-33500 AVideo Vulnerable to Stored XSS via Markdown `javascript:` URI Bypasses ParsedownSafeWithLinks Sanitization
Attackers can inject stored XSS via markdown links in comments due to sanitization bypass, potentially leading to session hijacking or malicious script execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-33500?
CVE-2026-33500 is a medium-severity cross-site scripting vulnerability in Wwbn Avideo, published on 23 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-33500?
2 open source packages ship an affected version, including wwbn/avideo. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
wwbn/avideo Packagist | All versions to 26.0 | None |
wwbn/avideo Packagist | All versions to 26.0 | None |
Products include Wwbn Avideo.
How do I fix CVE-2026-33500?
No fix has been published for CVE-2026-33500 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-33500 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33500 exists.
Other vulnerabilities in Wwbn Avideo
- CVE-2026-40911 WWBN AVideo YPTSocket WebSocket Broadcast Relay Leads to Unauthenticated Cross-User JavaScript Execution via Client-Side eval() Sinks
- CVE-2026-33478 AVideo Multi-Chain Attack: Unauthenticated Remote Code Execution via Clone Key Disclosure, Database Dump, and Command Injection
- CVE-2022-30534 Command injection in AVideo
- CVE-2022-30547 Path traversal in AVideo
- CVE-2022-32572 Command injection in AVideo
Sources
Also known as GHSA-72h5-39r7-r26j.