Microsoft has pulled dozens of open source repositories from GitHub while it investigates a breach that appears to have injected password-stealing malware into code used by AI developers. The incident, which security researchers say could expose passwords and other credentials, affects projects tied to Azure and developer tools used with AI coding apps such as Claude Code, Gemini’s command line interface, and VS Code.
Microsoft removes repositories during investigation
Microsoft confirmed to TechCrunch that it has “temporarily removed some repositories as we investigated potential malicious content.” The company said, “Some of these repos have been restored after review, while others may remain offline while work continues.” Microsoft also said that, “As part of our investigation, we notified a small number of customers who may have pulled down content from the affected repositories. We will continue to investigate, and if anything further is identified that requires customer action, we will reach out directly through our established support channels.”
When asked by TechCrunch, Microsoft did not immediately provide the specific number of customers affected. The company’s response followed a report first published by 404 Media.
On GitHub, where Microsoft owns the code-hosting platform, at least 70 Microsoft projects were shown as disabled, with a message saying: “Access to this repository has been disabled by GitHub Staff due to a violation of GitHub’s terms of service.”
What researchers say the malware did
Security firm Cloudsmith and the community-driven malware analysis site OpenSourceMalware were among the first to flag the incident. According to their findings, the malware was designed to steal users’ passwords and other sensitive credentials when they opened the compromised tools in AI coding applications.
That makes the compromise especially concerning for developers working in modern AI-assisted environments, where code snippets and project files may be opened, copied, or executed through tools that are connected to cloud systems and other sensitive services. The affected repositories included Microsoft projects related to Azure and tools used by developers building with AI coding applications.
It is not immediately known how many people downloaded the affected tools before Microsoft removed the repositories. That missing figure leaves open the scale of the possible exposure, including how many systems may have interacted with the compromised code.
Why this matters for developers
This incident fits a pattern that security experts have been watching closely in recent months: hackers targeting popular open source projects in order to distribute malware to large numbers of downstream users. These are known as supply chain attacks, because the attackers aim not only at one developer or one machine, but at code that may be reused broadly across products, teams, and cloud environments.
- Open source projects can reach many users quickly once a malicious change is introduced.
- Developers working in AI coding tools may expose higher-value credentials, including cloud logins and service tokens.
- Projects associated with major vendors can have especially wide distribution and trust.
In this case, the concern is not just that code was altered, but that the altered code may have been used in environments where developers routinely handle passwords and other secrets. That combination can make a breach more damaging than a typical malware incident.
A rare breach for a company of Microsoft’s size
Open source maintainers and smaller project owners are frequent targets of supply chain attacks, sometimes through long-running attempts to compromise trust, credentials, or build pipelines. It is far less common, however, for a company with Microsoft’s resources and security infrastructure to see its own open source projects compromised in this way.
The latest incident is also notable because it follows another recent breach involving Microsoft open source code. According to Ars Technica, this is Microsoft’s second known breach in the past few weeks that allowed hackers to compromise its open source projects. In mid-May, security researchers said Microsoft’s Durable Task project, which helps developers build apps, had been hacked.
OpenSourceMalware said the new incident is a “re-compromise” of the Durable Task project, suggesting either that Microsoft did not fully remove the attackers after the earlier breach or that a separate intrusion occurred. Microsoft has not publicly confirmed which of those explanations is correct.
What is known, and what is still unclear
Based on the available reporting, several points are confirmed: Microsoft removed or disabled a large number of GitHub repositories, researchers linked the code to password-stealing malware, and the company notified at least some customers who may have obtained the compromised content. Microsoft also said some repositories have been restored after review, while others may stay offline as the investigation continues.
Several key details remain unresolved. Microsoft has not said how the breach occurred, how many customers may have been affected, whether the malware was present in source code, build artifacts, or other distributed content, or whether the compromise extended beyond the repositories currently identified. The company also has not given a timeline for restoring all affected projects.
For users and developers who may have downloaded Microsoft open source tools recently, the practical concern is whether those downloads were made before the repositories were disabled and whether the tools were opened in AI coding environments that could trigger the malicious behavior described by researchers. Microsoft said it will contact customers directly if it identifies any further action required.
Part of a wider supply chain problem
The broader significance of the incident goes beyond Microsoft itself. Open source software is now embedded in much of modern software development, including AI-assisted coding workflows. That makes repository security and code integrity increasingly important, especially when tools interact with cloud accounts, authentication systems, and developer secrets.
Recent months have shown how attractive these targets are to attackers. A successful compromise of even a niche developer utility can cascade across teams and organizations if the tool is widely trusted or integrated into other systems. In that context, the Microsoft breach underscores a persistent challenge for the software industry: the same openness that makes open source powerful can also make it vulnerable when attackers succeed in slipping malicious code into the supply chain.
For now, Microsoft says the response is still ongoing. Some repositories are back online, others remain disabled, and the company says it continues to investigate. Security researchers, meanwhile, are still evaluating how far the malware may have spread and how many developers may have been exposed.
Source: Original report
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Last Modified: July 7, 2026 at 9:41 pm
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