Skip to content
Fencer Intel
medium 5.4

CVE-2026-33500 json

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

published 7mo ago modified 4mo ago also EUVD-2026-20065 , GHSA-72h5-39r7-r26j

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

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.

Patch / fix

Is CVE-2026-33500 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
7mo ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/WWBN/AVideo/security/advisories/GHSA-72h5-39r7-r26j referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
packagist wwbn/avideo
<=26.0
 no fix listed

Affected products

  • WWBN AVideo

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.