Microsoft announced an out-of-band reliability patch for Internet Explorer 11.
Exact details about the patch are unavailable, Microsoft only states that it improves the reliability of Internet Explorer 11 when you use it in Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2.
The page says that the file is available from Windows Update, but there are also manual download patches available for the 32-bit and 64-hit versions of Windows 8.1, along with another patch for Windows Server 2012 R2. The patch for Windows RT 8.1 is only available via Windows Update. While Microsoft is keeping details of what this IE11 patch fixes to itself, the support page does say that users must restart their PC after it is installed.