Blog: Microsoft Updates April 2013 - 3 Critical VulnerabilitiesMicrosoft released two Bulletins this month patching 3 critical vulnerabilities. Along with these immediate issues, they released five other rated "Important". It appears that the two Bulletins address use-after-free vulnerabilities that can all be attacked through Internet Explorer.
Source:
Blog: Microsoft Updates April 2013 - 3 Critical Vulnerabilities