The software giant, in an advisory, said it expects to release two patches on Tuesday: one aimed at development tools suite Visual Studio, the other for Internet Explorer.
Mike Reavey, group manager of the Microsoft Security Response Center, said in a blog post Friday that the update is meant to address a "single, overall issue" in all versions of Windows, but did not provide further details. Customers who currently are fully patched are protected against "known attacks" related to the issue, he said.
"While we can't go into specifics about the issue prior to the release, we can say that the Visual Studio bulletin will address an issue that can affect certain types of applications," Reavey wrote. "The Internet Explorer bulletin will provide defense-in-depth changes to Internet Explorer to help provide additional protections for the issues addressed by the Visual Studio bulletin."
In addition, the IE update will resolve a number of "critical" vulnerabilities, unrelated to Visual Studio, that previously had been privately disclosed.
Microsoft typically releases its security updates on the second Tuesday of the month. This marks the first time that the company has gone off cycle since December, when it pushed out an emergency fix for Internet Explorer.