BetaNews is reporting that UNIX developers at HBX Networks have found a bug in Gmail that, “allows access to other users’ personal e-mails. By altering the “From” address field of an e-mail sent to the service, hackers could potentially find out a user’s personal information, including passwords.” All of the details in the story: Gmail Bug Exposes E-mails to Hackers.
Postscript (from Danny): Google says they’ve now fixed this, with posts from them in the story above and at Slashdot: Gmail Messages Are Vulnerable To Interception.