# CVE-2026-16477: Insecure Deserialization of .cleanshot Files in CleanShot X


- **Severity:** High 8.4 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 22 Oct 2026
- **Updated:** 22 Oct 2026
- **Also known as:** GHSA-9gj2-4mhg-73v2

## What is CVE-2026-16477?

CVE-2026-16477 is a high-severity vulnerability in MTW CleanShot X, published on 22 Oct 2026. 

### Official description

CleanShot X for macOS insecurely deserializes untrusted data embedded in a .cleanshot project file (editable screenshot annotations). Exploitation requires an attacker to craft a malicious .cleanshot file, deliver it to the target, and have the target open it; the payload then executes automatically during parsing, resulting in arbitrary code execution in the context of the current user. Users who have never opened a .cleanshot file from an untrusted source are not affected by this vulnerability. This vulnerability was fixed in versions: 4.5.2, 4.6.3, 4.7.8 and 4.8.10

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-16477?


## How do I fix CVE-2026-16477?

No fix has been published for CVE-2026-16477 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-16477 being exploited?

There is no known exploitation of CVE-2026-16477 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16477 and fix it if it is affected.

What it is: CVE-2026-16477 is a high-severity vulnerability in MTW CleanShot X, published on 22 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-16477 in the wild and no public exploit code.

Affected product: MTW CleanShot X. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-16477/ (Markdown: https://insights.sbomify.com/CVE-2026-16477/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16477
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16477
- OSV: https://osv.dev/vulnerability/CVE-2026-16477

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16477/
Summaries are generated and may contain mistakes; the official description above is the record.