Microsoft says its Internet Explorer Web browser has a security flaw that could allow hackers to run programs on another user's computer.
The glitch causes Internet Explorer to open automatically specially coded attachments in e-mail without warning.
One outcome is that it could unleash programs that could do anything from sending users a harmless message to deleting files from their computers.
Microsoft says that its Internet Explorer versions 5.01 and 5.5 are affected, but it has developed a problem-solving "patch" that can be downloaded from the company's website.
Scott Culp, Microsoft's security program manager, says the flaw is contained in "a few" out of several hundred Multipurpose Internet Mail Extensions, or MIMEs, which are used to encode files as e-mail attachments.
He said it was a typical software error and was discovered before any viruses could be spread.
The company is currently working to install checks for the glitch on virus scanners for corporate customers.
The Seattle-based company was notified of the flaw by a security researcher in Spain who had found previous security gaps in Microsoft's Internet Explorer and Netscape Navigator.
PA