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Recent investigations have identified the BlueMoon exploit kit, used by espionage-driven threat activity clusters, particularly linked to APT31, a China-aligned state-sponsored group, since August 28, 2026. BlueMoon exploits three vulnerabilities: CVE-2026-85046 (a type confusion vulnerability in Google Chrome's V8 engine), an unassigned V8 sandbox escape, and CVE-2026-85880 (a heap-based buffer overflow in Windows ALPC). Google and Microsoft have released patches for these vulnerabilities, which were exploited as "patch-gap" zero-days. The attack vectors typically begin with phishing emails that lead victims to malicious URLs, triggering the vulnerabilities for code execution and privilege escalation. Variants of BlueMoon have been detected, featuring modifications for specific campaigns. Notable attack chains include: - APT31 targeting NGOs and mining firms in the U.S. with a malicious browser add-on called GemStone. - UNK_LateNight targeting U.S. aerospace companies, deploying BlueMoon alongside the ShadowPad backdoor. - UNK_DoubleCheck targeting a Vietnamese manufacturer, using DLL sideloading to execute a Rust binary. - UNK_QuietRacket targeting government and financial organizations in Indonesia and Singapore, modifying BlueMoon to execute a .NET assembly. CISA added the Chrome flaw to its Known Exploited Vulnerabilities catalog on September 4, 2026, requiring federal agencies to apply patches by September 18, 2026. Indicators of compromise include specific process trees, files, folders, scheduled tasks, mutexes, and registry keys. Proofpoint has released detection rules to help organizations identify and mitigate these threats.