Following the "Flame malware attack", which involved the use of a fraudulent Microsoft digital certificate, Microsoft has been looking at its certificates and found 28 are rubbish. Microsoft also released its new updater for certificates as a critical update for Windows Vista and later versions as part of today's July Patch Tuesday.
Redmond has not said what the now-untrusted certificates were used for, but company officials said there were a total of 28 certificates affected by the move. Many of the affected certificates are listed simply as "Microsoft Online Svcs". Microsoft said none of them had been compromised or used maliciously, it was just being safe rather than sorry.
As an extra precautionary measure, Microsoft released Security Advisory 2728973 today to announce the availability of a Critical, non-security update that moves several of these certificates into the Untrusted Certificate Store.