Hotmail users are now unable to log out of their account if the browser they are using does not accept third party cookies.
The move by Microsoft raises security concerns, particularly as PCs on corporate networks and in cybercafes and libraries are often set to reject cookies.
The error screen* that greets users who try to log out tells them they must re-enable third party cookies or close every browser window.
Third party cookies are most commonly used by advertising networks to track surfers across the web.
We've asked Microsoft what is behind its demand they are enabled, and whether it's considered the potential security implications. We'll update this story when it gets back to us.
Thanks to Reg reader Phil for spotting the change. ®
*Complete with typo.