# CVE-2025-66402: misskey.js's export data contains private post data

> Attackers can export private posts from favorites or clips without permission, exposing sensitive content to unauthorized users.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Dec 2025
- **Updated:** 16 Dec 2025
- **Also known as:** GHSA-496g-mmpw-j9x3

## What is CVE-2025-66402?

CVE-2025-66402 is a high-severity missing authorization vulnerability in misskey-dev misskey, published on 15 Dec 2025. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2025-66402?

2 open source packages ship an affected version, including misskey-js. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `misskey-js` | npm | From 13.0.0-beta.16 | 2025.12.0 |
| `misskey-js` | npm | From 13.0.0-beta.16 | 2025.12.0 |

Products: Misskey Misskey.

## How do I fix CVE-2025-66402?

Upgrade misskey-js to 2025.12.0 or later.

## Is CVE-2025-66402 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66402 exists.

## Other vulnerabilities in misskey-dev misskey

- [CVE-2025-25306](https://insights.sbomify.com/CVE-2025-25306/): Misskey's Incomplete Patch of CVE-2024-52591 Leads to Forgery of Federated Notes (critical 9.3)
- [CVE-2023-49079](https://insights.sbomify.com/CVE-2023-49079/): Misskey's missing signature validation allows arbitrary users to impersonate any remote user. (critical 9.3)
- [CVE-2026-28431](https://insights.sbomify.com/CVE-2026-28431/): Misskey lacks proper authorization checks and input validation (critical 9.2)
- [CVE-2023-52139](https://insights.sbomify.com/CVE-2023-52139/): Misskey vulnerable to improper authorization when accessing with third-party application (critical 9.1)
- [CVE-2024-52590](https://insights.sbomify.com/CVE-2024-52590/): Missing validation allows spoofed profiles in Misskey (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66402 and fix it if it is affected.

What it is: CVE-2025-66402 is a high-severity missing authorization vulnerability in misskey-dev misskey, published on 15 Dec 2025. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66402 exists.

Affected packages and fixed versions:
- misskey-js (npm): affected from 13.0.0-beta.16; fixed in 2025.12.0
- misskey-js (npm): affected from 13.0.0-beta.16; fixed in 2025.12.0

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-2025-66402/ (Markdown: https://insights.sbomify.com/CVE-2025-66402/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66402
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66402
- OSV: https://osv.dev/vulnerability/CVE-2025-66402

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-66402/
Summaries are generated and may contain mistakes; the official description above is the record.