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

Severity: high (CVSS 8.4 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-22 · updated 2026-10-22
Weakness: CWE-502

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

Affected products

MTW CleanShot X: from 4.0.0 before 4.5.2; from 4.6.0 before 4.6.3; from 4.7.0 before 4.7.8; from 4.8.0 before 4.8.10 — fixed in 4.5.2, 4.6.3, 4.7.8, 4.8.10

How to fix

Upgrade to a fixed version: MTW CleanShot X 4.5.2, 4.6.3, 4.7.8, 4.8.10. Check the vendor advisory for mitigations.

References

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