Microsoft on Thursday said that its monthly security patch, to be issued on Tuesday, February 9th, will include 13 security bulletins.

That's the largest number of security bulletins issued in February for the past four years, according to Sheldon Malm, senior director of security strategy at Rapid7.

Next week's patch is scheduled to include five "critical" bulletins. Two of the bulletins affect Microsoft Office, and eleven affect Microsoft Windows.

Malm notes that all of Microsoft's operating systems, including Vista and Windows 7, will get fixes. "I won't be surprised if Microsoft is playing catch-up on some lingering vulnerabilities from last year," he said in an e-mailed statement.

One vulnerability that won't be fixed this month can be found in Internet Explorer. Microsoft on Wednesday issued a security advisory, stating that it is investigating a publicly reported vulnerability in versions of its Web browser.

"Our investigation so far has shown that if a user is using a version of Internet Explorer that is not running in Protected Mode an attacker may be able to access files with an already known filename and location," Microsoft's advisory says.

Core Security says that in order to exploit the Internet Explorer vulnerability, an attacker would only have to entice a user to click on a URL or visit a malicious Web site, without any other interaction. A successful attacker would gain the ability to read files on the user's system but couldn't run arbitrary code without restrictions.

Microsoft lists a number of mitigating factors which could limit attempts to exploit this vulnerability.

Last month, Microsoft issued an emergency, or out-of-band, security patch for Internet Explorer. The patch addressed a vulnerability said to have been used in a cyber attack from China on Google and a number of other companies.