Mine was for a French social networking site 4 years ago. They used to send mails everyday to say "hey look at the people who you might know". The links on the

Mine was for a French social networking site 4 years ago. They used to send mails everyday to say "hey look at the people who you might know". The links on the mail would automatically log the user on the website. When I sent the code live it took 2 days (and more than 50000 mails to found out that when I sent a mail to person Z about person Y the link logged in Z ON Y's account. [1] I knew it was a bad idea to automatically log on the target of the mail. But it was the policy. And it still the case as far as I know. And if you forgot your password don't worry It's stored in plaintext...