In short
- CVE-2025-66402 is a MEDIUM (CVSS 6.5) vulnerability affecting misskey (misskey), misskey-js.
- Chance of exploitation in the next 30 days (EPSS): 0.31%, higher than 24.3% of all vulnerabilities.
- Fix: update to 2025.12.0 or later.
| Package | Affected versions | Patched versions |
|---|
| misskey | = 13.0.0≥ 13.1.0, < 2025.12.0
| 2025.12.0
|
| misskey-js npm | ≥ 13.0.0-beta.16, < 2025.12.0
| 2025.12.0
|
Description
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.
NVD description
Misskey is an open source, federated social media platform. Starting in version 13.0.0-beta.16 and prior to version 2025.12.0, an actor who does not have permission to view favorites or clips can can export the posts and view the contents. Version 2025.12.0 fixes the issue.
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