To keep GitHub as secure as possible for every user, we will remove RC4 support in our SSL configuration on
github.com and in the GitHub API on January 5th 2015.

RC4 has a number of cryptographic weaknesses that may be exploited, impacting the security of your data. More details about these vulnerabilities are listed in the current IETF draft.

If you are using Internet Explorer on Windows XP, you will no longer be able to access github.com once this change takes place. Windows XP only supports outdated SSL ciphers, is no longer supported by Microsoft, and contains a known critical security problem in its SSL implementation.

We strongly recommend that Windows XP users upgrade to a newer version of Windows. If this is not possible, you will need to use Chrome or Firefox to access GitHub on Windows XP. The git client available at git-scm.com still works on Windows XP.