# 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.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **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 available:** No
- **Published:** 23 Mar 2026
- **Updated:** 24 Mar 2026
- **Also known as:** GHSA-72h5-39r7-r26j

## 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 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-33500?

2 open source packages ship an affected version, including wwbn/avideo. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `wwbn/avideo` | Packagist | All versions to 26.0 | None |
| `wwbn/avideo` | Packagist | All versions to 26.0 | None |

Products: 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.

## 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](https://insights.sbomify.com/CVE-2026-40911/): WWBN AVideo YPTSocket WebSocket Broadcast Relay Leads to Unauthenticated Cross-User JavaScript Execution via Client-Side eval() Sinks (critical 10.0)
- [CVE-2026-33478](https://insights.sbomify.com/CVE-2026-33478/): AVideo Multi-Chain Attack: Unauthenticated Remote Code Execution via Clone Key Disclosure, Database Dump, and Command Injection (critical 10.0)
- [CVE-2022-30534](https://insights.sbomify.com/CVE-2022-30534/): Command injection in AVideo (critical 9.9)
- [CVE-2022-30547](https://insights.sbomify.com/CVE-2022-30547/): Path traversal in AVideo (critical 9.9)
- [CVE-2022-32572](https://insights.sbomify.com/CVE-2022-32572/): Command injection in AVideo (critical 9.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33500 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33500 exists.

Affected packages and fixed versions:
- wwbn/avideo (Packagist): affected all versions up to 26.0; no fix listed
- wwbn/avideo (Packagist): affected all versions up to 26.0; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33500/ (Markdown: https://insights.sbomify.com/CVE-2026-33500/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33500
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33500
- OSV: https://osv.dev/vulnerability/CVE-2026-33500

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33500/
Summaries are generated and may contain mistakes; the official description above is the record.