Microsoft has denied that there is a security hole in the User Account Control (UAC) feature of Windows 7 after a blogger reported it last week and posted what he said was a fix for it.

"I can tell you that this is not a vulnerability," a spokesman for Microsoft through its public relations team said in an email.

Last week, Long Zheng, a long-time Microsoft watcher and blogger, wrote on his I Started Something Blog that a change Microsoft made in Windows 7 to improve the UAC security feature has left the new OS less secure because it allows someone to remotely turn the feature off without the user knowing.

Zheng said that the new UAC default setting, which does not notify a user when changes are made to Windows settings, is where the security risk lies. A change to UAC is seen as a change to a Windows setting, so a user will not be notified if UAC is disabled, which Zheng said he was able to do remotely with some keyboard shortcuts and code.

However, Microsoft is standing by the change to UAC's default setting, saying it was the result of "a great deal of usability feedback on UAC prompting behaviour," and that the feature cannot be exploited unless there is already malicious code running on the machine and "something else has already been breached."

"The intent of the default configuration of UAC is that users don't get prompted when making changes to Windows settings," the spokesman said. "This includes changing the UAC prompting level."

UAC has been a controversial feature since Microsoft introduced it in Windows Vista to improve its security and give people who are the primary users of a PC more control over its applications and settings. The features prevents users without administrative privileges from making unauthorised changes to a system.

Windows 7 has been in public beta for about a month and not expected to ship until early next year. However, Microsoft said Friday the next release of the OS would be a nearly final release candidate and not another beta release, so some believe it will be out before the end of 2009.