Among the security patches released by Microsoft today is an Internet Explorer fix that is now being distributed for the third time, due to problems that weren't fixed on the patch's first or second releases, the company has admitted.

Last month, eEye Digital Security warned users that Microsoft's August security update, MS06-042, had in fact introduced a new critical security bug. Microsoft responded with a 'hotfix' repairing the problem.

The two companies also engaged in a war of words over eEye's disclosure of the seriousness of the problem introduced by MS06-042. While Microsoft described the problem as relatively minor, involving browser crashes, eEye discovered that the hole could be exploited to run malicious code. Microsoft called this disclosure "irresponsible" and removed eEye from the flaw credits.

That wasn't the end of the story, however: the 'hotfix' of 24 August failed to completely fix the problem, eEye discovered. This week's second update fixes the problems missed by the first re-release, Microsoft said.

"With the increased scrutiny this release received, a security researcher responsibly disclosed to us that a similar vulnerability was also discovered in IE5.01 on Windows 2000, IE 6.0 SP1 (in a different location), and the original release of Windows Server 2003 (not SP1)," said Microsoft group product manager Tony Chor, on the IE Blog.

"This release and the need for subsequent re-releases have certainly been a learning experience for us," he added. "This update cycle has not been an example of our best work."

Also this week, Apple urged users to upgrade to a new version of QuickTime that fixes a total of seven security holes. Current versions of QuickTime expose Macs and PCs to serious security vulnerabilities, Apple said.

Apple warned that QuickTime is vulnerable to an attack via specially crafted movies using the H.264 video codec standard. The malicious files can cause an integer overflow or buffer overflow that can crash the application and allow malicious code execution with the privileges of the user, according to Apple.

A separate bug can also crash the application and allow arbitrary code execution, Apple said. The bugs are fixed in QuickTime 7.1.3, available from Apple's site.