Vulnerability · Published Oct 22, 2026 · Assigned by CERT-PL

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

High 8.4

In plain English

A high-severity unsafe deserialization in CleanShot X from MTW. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).

Severity (CVSS 4.0)8.4High

Exploit odds (30 days)0.3%top 78.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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

Affected products (as reported)

Vendor	Product	Versions
MTW	CleanShot X	4.0.0 – before 4.5.24.6.0 – before 4.6.34.7.0 – before 4.7.84.8.0 – before 4.8.10

Weakness: CWE-502 · Vector: 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

References

https://cert.pl/en/posts/2026/10/CVE-2026-16477 third-party-advisory
https://cleanshot.com/ product