TL;DRThe Miasma worm hit 73 Microsoft GitHub repos across Azure and Microsoft orgs. It plants payloads that trigger in AI coding tools like Claude Code and Cursor.
The self-replicating Miasma worm has reached Microsoft‘s own GitHub repositories. GitHub disabled 73 repositories across four Microsoft organisations, including Azure, Azure-Samples, Microsoft, and MicrosoftDocs, after the worm planted malicious code that harvests developer credentials. It is the most significant escalation yet in an ongoing supply chain attack campaign that has been spreading across the open-source ecosystem for weeks.
The attack exploited previously compromised credentials. Last month, the threat group TeamPCP infected the “durabletask” PyPI package hosted in Microsoft’s Azure organisation to deliver an information stealer. Security researcher Paul McCarty pointed out that the same repository is at the centre of this month’s takedown.
“When the repo at the root of last month’s compromise is the hub of this month’s takedown, that is not a coincidence, that is the same wound reopening,” McCarty said. “Whoever held those credentials in May plausibly never fully lost them.”
What makes this campaign particularly dangerous is how the payload detonates. The attacker planted a 4.3 MB payload runner wired to execute automatically through five developer tools: Claude Code, Gemini CLI, Cursor, VS Code, and the npm test script. A developer only needs to clone an affected repo and open it in an AI coding agent for the malware to run.
