Microsoft Open Source Packages Compromised with Credential-Stealing Code for Second Time in Weeks

On June 5, GitHub's automated detection systems disabled 73 Microsoft repositories across four organizations — Azure, Azure-Samples, microsoft, and MicrosoftDocs — within 105 seconds of detecting signs of the Miasma worm, a credential-stealing malware descended from the Mini Shai-Hulud toolkit open-sourced by cybercrime group TeamPCP. The attack began when a compromised contributor account pushed a malicious commit to Azure/durabletask, dropping configuration files that triggered remote code execution when developers opened the repo in AI coding tools such as Claude Code, Gemini CLI, VS Code, or Cursor. The malware harvested credentials from AWS, Azure, GCP, Kubernetes, password managers, and over 90 developer tool configurations, then spread laterally through cloud infrastructure. Security researchers at StepSecurity noted the attack appears to be a re-compromise of the same durabletask project hit in May 2025, suggesting Microsoft failed to fully rotate the GitHub Actions secrets stolen in that earlier breach. The Azure org bore the heaviest impact, losing 49 repositories, and every workflow referencing Azure/functions-action@v1 stopped resolving, breaking CI/CD pipelines for an unknown number of developers. Microsoft initially described the takedowns only as a 'terms of service violation' before later acknowledging it was investigating 'potential malicious content'; by June 10, the company stated all repos had been restored and that a small number of affected customers had been notified.