CleanShot X EUVD-2026-108208

Exploitation requires that the target have CleanShot X installed on macOS and that they open a .cleanshot project (editable screenshot annotation) file originating from an attacker-controlled or untrusted source; parsing/deserialization of that file triggers automatic payload execution with no further privileges needed (PR:N). The key limiting factors are mandatory user interaction (UI:A - the victim must receive and actively open the malicious file, so delivery depends on social engineering), local file delivery rather than a network-exposed service (AV:L), and version - systems updated to 4.5.2, 4.6.3, 4.7.8, or 4.8.10 are fixed. The description explicitly notes that users who never open a .cleanshot file from an untrusted source are not affected, which is the single most important scoping condition for defenders.

This is a genuine but interaction-gated risk rather than a remotely-wormable emergency. The CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:N/UI:A) scoring 8.4 is internally consistent with the description: a CWE-502 insecure-deserialization flaw where a crafted .cleanshot file executes code automatically during parsing, yielding high confidentiality, integrity and availability impact (VC:H/VI:H/VA:H) in the current user's context. The decisive limiter is UI:A - the victim must obtain and open an attacker-supplied file - which is why the vector is AV:L (file-delivery) rather than AV:N, and which caps real-world risk despite the high impact. No EPSS score was provided, so exploitation probability cannot be quantified. CISA KEV status is not indicated (treat as not listed), and no proof-of-concept or exploit reference is present in the supplied data - only the CERT-PL advisory and the vendor homepage. SSVC/decision signals point to 'this_week' priority (not act_now or emergency), reinforcing that this is a near-term patch item, not a drop-everything fire. Net: a real priority for environments running CleanShot X, driven by trivial technical exploitation once a file is opened, but bounded by the social-engineering requirement and the absence of any evidence of active exploitation or public exploit code.

An attacker crafts a malicious .cleanshot annotation project file embedding a serialized payload and delivers it to a macOS CleanShot X user via email, chat, or a shared link disguised as a legitimate screenshot project. When the victim opens the file, CleanShot X deserializes the untrusted data during parsing and the payload runs automatically, giving the attacker arbitrary code execution as that user. No public exploit code was identified in the supplied sources at the time of analysis.