Microsoft is beginning the process of discontinuing support for digital certificates that use the MD5 hashing algorithm. The private keys used in these certificates can be derived and could allow an attacker to duplicate the certificates and use them fraudulently to spoof content, perform phishing attacks, or perform man-in-the-middle attacks. The MD5 cryptographic hash function has long been considered insecure for use in SSL certificates and digital signatures. Microsoft recommends that customers download, test, and apply the update at the earliest opportunity.
Source: https://thehackernews.com/2013/08/Microsoft-MD5-hashes-digital-certificates-RDP-Authentication.html