Thousands of GitHub repositories exposed via Microsoft Copilot

• Copilot has access to private GitHub repositories, researchers found
• The repositories were public at some point, and Bing cached them
• The caching behavior is "acceptable" says Microsoft

Thousands of private GitHub repositories, some of which possibly contained credentials and other secrets, are being exposed through Microsoft Copilot, the company’s Generative Artificial Intelligence (GenAI) virtual assistant, experts have warned.

Cybersecurity researchers from Lasso reported their findings to Microsoft but got a mixed response.

Lasso is a cybersecurity company focusing on threats emerging from the use of new AI tools, and reported Copilot was able to retrieve one of its own GitHub repositories which should have been private and inaccessible on the wider internet. Indeed, navigating directly to GitHub returns a “page not found” error. However, at one point the team mistakenly left the repository public for a short period of time - long enough for Microsoft’s Bing search engine to index it. That allowed Copilot access to the data, even though it shouldn’t have.

Severe implications

Lasso further investigated, compiling a list of tens of thousands of repositories that were public at one point, and set to private today, finding more than 20,000 which can still be accessed through Copilot, belonging to tens of thousands of organizations, including some of the technology sector’s biggest players.

The implications of the findings could be quite severe. Speaking to TechCrunch, Lasso’s co-founder Ophir Dror said it used the flaw to retrieve a GitHub that hosted a tool allowing them to create “offensive and harmful” AI images using MIcrosoft’s cloud AI service. Different company secrets could also be exposed this way, prompting Dror to advise victims to rotate or revoke their keys.

Microsoft allegedly told the company that the issue is “low severity” and that the caching behavior was “acceptable.” However, as of December 2024, Microsoft no longer includes links to Bing’s cache in its search results. Copilot can still access the data.

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