Microsoft has admitted that the latest versions of MSN Messenger are vulnerable to computer hackers.
The flaw, described as "critical", is the latest to be discovered by the Redmond giant after the launch of its campaign to stamp out security problems.
Microsoft admitted that hackers could exploit a feature that allows users to gather in a single virtual location, or chat room, to exchange messages across the internet in real time.
The feature can be exploited to allow malicious commands to be executed on a user's computer.
MSN Chat Control, MSN Messenger versions 4.5 and 4.6, and Exchange Instant Messenger 4.5 and 4.6 are affected by the glitch.
The discovery is an embarrassment for Microsoft, and will certainly not help in its aim to replace AOL's Instant Messenger as the most popular chat tool.
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