Researcher releases unofficial IE fix for URI bug

A security researcher has beaten Microsoft to the punch with the release of an unofficial patch for an Internet Explorer 7 bug.

The unofficial update targets a Universal Resource Identifier (URI) vulnerability that Microsoft acknowledged last week, after months of maintaining that the flaw stemmed from the security shortcomings in third-party software. Any changes Microsoft made might cause third-party applications to malfunction by breaking protocol handlers, the company argued.

Microsoft revised its opinion last Thursday in light of a revised risk assessment of the danger posed by the flaw, which concluded that it needed to tighten up its URI handling code.

But before Redmond could get an update out the door Hyperion (AKA Hackbunny) stepped in with an unofficial fix. Users who apply the 16KB update do so at their own risk, he warns. Microsoft has strongly urged users to stay clear of unofficial patches in the past and can be expected to do the same again with Hyperion's update.

Redmond's planned patch, whose release date remains unclear, is targeted at Windows Server 2003 and Windows XP with Internet Explorer 7 installed. Vista

URI handling facilitates data sharing between applications making it possible, for example, to click on a mailto link in IE that launches a user's default email client, inserting an appropriate email address and subject line.

Speakers at the Toorcon hacking conference in San Diego last weekend warned of the possibility that Mac and Linux systems, like Windows, might be susceptible to URI flaws. Nathan McFeters, a security consultant at Ernst & Young, has yet to identify specific exploits but has discovered some potential candidates for further research. ®