Headline

GHSA-496g-mmpw-j9x3: misskey.js's export data contains private post data

Summary

After adding private posts (followers, direct) that you do not have permission to view to your favorites or clips, you can export them to view the contents of the private posts.

PoC

Create an account (X) for testing and an account (Y) for private posts on the same server.
Send appropriate content from Y using “Follow”
Send appropriate content to any user using “Nominate” from Y
Obtain the URLs for the two posts above using Y’s account.
Query the URLs for the two posts using X and add them to your favorites or clips.
Export your favorites or clips using X.
Check the exported data.

Note: Verified in v2025.11.1

Impact

This could allow an attacker to view the contents of private posts. If you have pinned private posts, this could be a real problem, as the ID of the private post can be obtained by viewing the user page on the original server.

9 hours ago

ghsa

Open in Source

#nodejs #js #git

GitHub Advisory Database
GitHub Reviewed
CVE-2025-66402

misskey.js’s export data contains private post data

High severity GitHub Reviewed Published Dec 13, 2025 in misskey-dev/misskey • Updated Dec 15, 2025

Package

npm misskey-js (npm)

Affected versions

>= 13.0.0-beta.16, < 2025.12.0

Patched versions

2025.12.0

Summary

After adding private posts (followers, direct) that you do not have permission to view to your favorites or clips, you can export them to view the contents of the private posts.

PoC

Create an account (X) for testing and an account (Y) for private posts on the same server.
Send appropriate content from Y using “Follow”
Send appropriate content to any user using “Nominate” from Y
Obtain the URLs for the two posts above using Y’s account.
Query the URLs for the two posts using X and add them to your favorites or clips.
Export your favorites or clips using X.
Check the exported data.

Note: Verified in v2025.11.1

Impact

This could allow an attacker to view the contents of private posts.
If you have pinned private posts, this could be a real problem, as the ID of the private post can be obtained by viewing the user page on the original server.

References