This security update resolves two privately reported vulnerabilities and one publicly disclosed vulnerability in Microsoft .NET Framework. The most severe of the vulnerabilities could allow remote code execution if a user visits a website containing a specially crafted OpenType font (OTF) file using a browser capable of instantiating XBAP applications.
This security update is rated Critical for Microsoft .NET Framework 3.0 Service Pack 2, Microsoft .NET Framework 3.5, Microsoft .NET Framework 3.5.1, Microsoft .NET Framework 4, and Microsoft .NET Framework 4.5 on affected editions of Microsoft Windows; it is rated Important for Microsoft .NET Framework 2.0 Service Pack 2 and Microsoft .NET Framework 3.5 Service Pack 1 on affected editions of Microsoft Windows.
The security update addresses the vulnerabilities by ensuring that the .NET Framework properly handles OpenType fonts, XML digital signatures, and document type definitions in JSON data encodings. For more information about the vulnerabilities, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the next section,Vulnerability Information.
Recommendation. Most customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.
For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update immediately using update management software, or by checking for updates using the Microsoft Update service.