We recently reported on a serious vulnerability affecting all versions of Internet Explorer that is being exploited on the web.

Well, it appears that Microsoft sees this vulnerability as very serious, because they are planning to release an update – later today – that addresses the problem. This is an ‘out-of-band’ update, meaning that it’s considered too important to wait for the next Patch Tuesday.

Just in case you were wondering, this vulnerability affects all versions of Internet Explorer on all versions of Windows, including Windows XP. But the patch will not be made available for Windows XP computers.

Update 2014May02: Surprisingly, Microsoft has decided to make this update available for Windows XP. I confirmed this by running Microsoft Update on my WinXP test system: security update 2964358 was offered, and I installed it without any difficulties. Reading through the associated bulletin (MS14-021) there is no explanation for this decision, but there is confirmation, in the section titled “Security Update Deployment
– Windows XP (all editions)”, and in a related post on the MSRC blog. The Verge has additional details, as does Ars Technica. The Ars Technica post includes the official explanation from Microsoft:

Even though Windows XP is no longer supported by Microsoft and is past the time we normally provide security updates, we’ve decided to provide an update for all versions of Windows XP (including embedded) today. We made this exception based on the proximity to the end of support for Windows XP. The reality is there have been a very small number of attacks based on this particular vulnerability and concerns were, frankly, overblown. Unfortunately this is a sign of the times and this is not to say we don’t take these reports seriously. We absolutely do.

Update 2014May02: Another Ars Technica post makes the argument that releasing a patch for Windows XP was a mistake. The moment of truth will be Patch Tuesday for May 2014: will Microsoft stick to its guns and leave Windows XP out of the next set of patches?