Multiple espionage-motivated threat activity clusters have been found deploying a previously undocumented exploit kit called BlueMoon that chains together multiple vulnerabilities in Microsoft Windows and Google Chrome.

The first in-the-wild use of BlueMoon has been attributed to the China-aligned state-sponsored group tracked as APT31 (aka Bronze Vinewood, Judgement Panda, JungleBamboo, PerplexedGoblin, RedBravo, TA412, Tide Castle, and Violet Typhoon) on August 28, 2026.

“Within days, several other espionage-motivated clusters began using BlueMoon, the majority of which have a suspected China nexus,” Proofpoint said in a report published today. “However, BlueMoon may not be exclusive to China-aligned actors, as some usage remains unattributed and there are also potentially more actors using the exploit kit.”