Microsoft has warned of a Windows zero-day vulnerability, affecting all versions of the operating system.
The Redmond giant said it had seen a proof-of-concept attempting to exploit the vulnerability, which could conceivably harm Internet Explorer users on Windows.
Nothing has been seen yet in the wild.
The flaw resides in the MIME Encapsulation of Aggregate HTML protocol handler, used by applications to render certain kinds of documents.
"An attacker could construct an HTML link designed to trigger a malicious script and somehow convince the targeted user to click it," Angela Gunn, from Microsoft's Trustworthy Computing division, hypothesised in a blog post.
"When the user clicked that link, the malicious script would run on the user's computer for the rest of the current Internet Explorer session. Such a script might collect user information (e.g. email), spoof content displayed in the browser, or otherwise interfere with the user's experience."
A patch has not yet been offered but Microsoft has issued a workaround in its advisory for administrators to ensure nothing goes awry.
"The workaround we are recommending customers apply locks down the MHTML protocol and effectively addresses the issue on the client system where it exists," Gunn added.
"We are providing a Microsoft Fix-it package to further automate installation."
Microsoft did not confirm when a patch would be released, but said it was working on an update to address the vulnerability.
Just earlier this month, Microsoft warned about yet another zero-day flaw affecting Windows.
The vulnerability, affecting the Windows Graphics Rendering Engine, could have allowed malware to be installed on a computer if users viewed a malicious image in a browser or document.
