Despite a known browser vulnerability and lacking security support, Windows XP remains the second most popular PC operating system, according to NetApplications.

While the use of XP has been dwindling since January, it's still the OS of choice for 26% of PCs, the stat-gathering firm says in its most recent update.

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That puts it behind Windows 7 with 49% but still way ahead of Windows 8 and Windows 8.1 combined, which total 12.24%, the company says.

After months of Microsoft campaigning to transition XP users to Windows 7, 8 or 8.1, in January XP still held 29% of users. The percentage actually rose in February by .23%, then dipped by 1.84% in March and dipped another 1.4% in April.

The popularity remains in the face of a zero day vulnerability discovered over the weekend that threatens users of Internet Explorer 6, the browser bundled with XP. Microsoft has said it won't provide a patch for the vulnerability for XP machines, but relented in this case.

The browser problem is the first known major security issue to crop up since Microsoft cut off support for XP on April 8. The security posture of the operating system will only worsen over time as attackers inevitably discover more and more vulnerabilities that then remain unpatched.

Tim Greene covers Microsoft and unified communications for Network World and writes the Mostly Microsoft blog. Reach him at [email protected] and follow him on Twitter @Tim_Greene.

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