The Hacker News infrom that the Gentoo Linux project's github account was hacked yesterday (June 28, 2018). Malware was placed in the code.
Developers reported about the problem as soon as it was discovered and cut off access. The malware has been removed from the code, but the system's developers recommend refraining from downloading anything from their repository until a full code review is completed.
Many companies use variations of Linux for various purposes. If you updated Gentoo source code after June 27, the only safe solution is to disable such systems, restore the version before June 28, 2018, and fully review the logs.