Miasma worm poisoned Microsoft repos to hijack AI coding agents

Microsoft, disclosed 5 Jun 2026. Manipulated AI Data exposed High

A self-replicating worm spread through more than 70 Microsoft and Azure GitHub repositories, planting config files that make Claude Code, Gemini CLI, Cursor and VS Code run a credential stealer when a developer opens the repo. GitHub disabled 73 repositories within minutes.

Disclosed

5 Jun 2026

Organization

Microsoft

Vendor

Multiple models

Product

Claude Code, Gemini CLI, Cursor

Type of AI

Coding assistant

How it happened

Manipulated AI: Agent hijack

Harm

Data exposed

Data involved

Credentials

Reach

Many organizations

Severity

High

Model at fault

No

Status

Confirmed

Sources

1. https://www.stepsecurity.io/blog/miasma-worm-hits-microsoft-again-azure-functions-action-and-72-other-repositories-disabled-after-supply-chain-attack-targeting-ai-coding-agents
2. https://www.govinfosecurity.com/miasma-worm-hits-microsofts-ai-coding-ecosystem-a-31912