A critical security loophole in a Microsoft GitHub repository could have allowed hackers to hijack automated systems and steal sensitive data, according to new data from Tenable Research.
The flaw, which carries a nearly perfect CVSSv4 score of 9.3, was found in the windows-driver-samples repository. With 7,700 stars and 5,000 forks, the project is a major hub for global developers. Researchers discovered that a simple Python string injection flaw turned the repository’s own automation scripts against it.
“The CI/CD infrastructure is part of an organization’s attack surface and software supply chain,” said Rémy Marot, staff research engineer at Tenable. “Without strong safeguards, a vulnerability in a pipeline can be exploited to trigger large-scale supply chain attacks and have critical impacts on downstream systems and users.”
The vulnerability lived within a GitHub Action, which is an automated script designed to run tasks. An attacker could have triggered this by opening a standard GitHub issue, which is a feature available to anyone with an account. By hiding malicious Python code inside the issue description, the attacker triggers a workflow that runs automatically. This execution happens on Microsoft’s infrastructure, allowing the hacker to steal the GITHUB_TOKEN. This digital key grants control over the repository.
Because this repository was created before 2023, the token likely held broad read and write permissions by default. This would have let an unauthorized user modify content or pose as Microsoft online. This discovery highlights a growing trend in cyberattacks which target the software supply chain. When a pipeline is compromised, every user downstream is at risk.
To stay safe, Tenable recommends that organizations restrict token permissions, audit automated workflows for injection risks, and treat their build pipelines as high-security zones.