On Monday, Lapsus$ through Telegram revealed that they had managed to breach some Microsoft DevOps accounts, and even went a step further to share a screenshot to support their claims. However, the screenshot was deleted shortly after being released.
Yesterday, the hackers leaked a torrent for a 9 GB 7zip archive containing the source code of over 250 projects, which they allegedly claim to belong to Microsoft. The release contained 90% of the source code for Bing, and 45% of the code for Bing Maps and Cortana. (via BleepingComputer)
Even though they say only some of the source code was leaked, the uncompressed archive contains approximately 37GB of source code allegedly belonging to Microsoft.
Microsoft is yet to give an official statement in regards to the matter, however, they are aware of the situation and are currently investigating the matter. Lapsus$ is also said to be behind Samsung's and Ubisoft's attacks.