Microsoft Copilot accesses deleted private GitHub repositories via Bing cache
Israeli cybersecurity firm Lasso reported that Microsoft Copilot could access the historical content of over 20,000 GitHub repositories that had been made private or deleted after being publicly indexed. The vulnerability stemmed from Bing search engine caching and affected organizations including Microsoft, Amazon AWS, Google, IBM, PayPal, and Tencent.
What happened
Lasso, an Israeli cybersecurity company, discovered that Microsoft Copilot could access historical data from GitHub repositories even after developers had made them private. According to Lasso co-founder Ophir Dror, when a repository that had been briefly public in 2024 was returned to private status, returning 404 errors to direct access attempts, the code remained accessible through Copilot.
Investigation revealed that over 20,000 GitHub repositories that were deleted or made private after being publicly indexed in 2024 retained their data within Copilot. The issue originated from Bing search engine's indexing and caching mechanisms. Although Microsoft disabled Bing's cache function in December 2024, Lasso stated that Copilot could still access data that should not have been public.
Reported impact
The vulnerability affected more than 1.6 million organizations including Microsoft, Amazon AWS, Google, IBM, PayPal, and Tencent. Exposed data included intellectual property, corporate sensitive information, and credentials.
Microsoft classified the issue as 'low risk' and described its caching behavior as 'acceptable.'
Index analysis
The vulnerability resulted from Bing search engine caching and indexing public repositories. When repositories were later made private or deleted, Copilot retained access to the cached data.
Classification
Sources and evidence
Sources not yet published
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