Facebook has put developers on notice that as of Oct. 1, apps that do not support SHA-2 will no longer connect to its network. The tech giant has fallen in line with Google, Mozilla and Microsoft in deprecating the SHA-1 and older hash algorithms. Experts have predicted that a practical collision attack against SHA 1 would be possible by 2018. Facebook said it plans to update its servers to stop accepting SHA 1 three months before a sunset date of January 1, 2016 established by the CA/Browser Forum. Google was next to phase out SHA 1 starting with Chrome 40.
Source: https://threatpost.com/facebook-requires-sha-2-as-of-oct-1/113131/