Miasma Worm Hits 73 Microsoft GitHub Repositories in Major Supply Chain Attack
A self-replicating supply chain worm has hit 73 Microsoft GitHub repositories across four organizations. The campaign also keeps mutating and spreading through open-source and developer tooling channels.
Intelligence analysis by GPT-5.4 Mini
Microsoft’s GitHub footprint has been caught up in the Miasma worm campaign, with 73 repositories affected across Azure, Azure-Samples, Microsoft, and MicrosoftDocs. The article says the worm keeps evolving, reusing stolen credentials and legitimate publishing paths to spread through trusted software channels.
A bad worm has been sneaking into software filing cabinets that developers trust. It copies itself from one place to another by acting like a real update, like a fake library book with a real-looking stamp.
Analysis
What happened
The article says Microsoft’s GitHub repositories were the latest target of the ongoing Miasma self-replicating supply chain attack. According to OpenSourceMalware, 73 repositories across four Microsoft GitHub organizations were impacted: Azure, Azure-Samples, Microsoft, and MicrosoftDocs. GitHub disabled access to the affected repositories.
Why this attack stands out
The reporting links Miasma to a variant of the Mini Shai-Hulud worm that TeamPCP publicly released in mid-May 2026. The worm is described as continuing to mutate, with new public repositories created to hold stolen secrets under multiple related descriptions, including “Miasma: The Spreading Blight” and “Hades - The End for the Damned.” The article says there were 13 repositories using the Hades description and 82 using the other naming patterns at the time of writing.
Evidence of broader spread
The campaign is not limited to npm registry abuse. SafeDep said malicious code was pushed directly into icflorescu/mantine-datatable and four related repositories, where a 4.3 MB payload runner was added and set to execute through Claude Code, Gemini CLI, Cursor, VS Code, and the npm test script. The article says the attack triggers when a developer clones an affected repository and opens it in an AI coding agent.
What the article argues
Security researchers quoted in the piece say the worm works through legitimate channels rather than exploiting a software bug in npm or GitHub. In that framing, the core weakness is the trust model itself: once a maintainer account or signing key is compromised, malicious updates can look like ordinary releases. The article presents this as one of the most significant and sustained supply chain campaigns seen so far.
Key points
- 73 Microsoft repositories were impacted across Azure, Azure-Samples, Microsoft, and MicrosoftDocs.
- GitHub disabled access to the affected repositories after the incident.
- Researchers say Miasma is a variant of the Mini Shai-Hulud worm released in mid-May 2026.
- The campaign can spread through trusted channels rather than exploiting a GitHub or npm vulnerability.
- SafeDep says malicious code was also pushed directly into several GitHub repositories and could trigger in AI coding tools.
GitHub’s disabling of affected repositories may slow the worm’s spread and limit further reuse of the compromised assets. The article also shows researchers are actively tracking the campaign’s variants and naming patterns, which can help defenders spot and block it sooner.
The article suggests the worm keeps mutating and can spread through legitimate publishing paths, so cleanup may not stop future waves. If stolen credentials or trusted maintainer accounts remain exposed, the same pattern could keep resurfacing across more repositories and packages.
