Facebook has fixed the bug that allowed a spamming worm to automatically posts messages to users’ walls earlier this week. The messages purported to be from friends who had found shopping bargains at Best Buy and Wal Mart. Computerworld reports, the flaw was the second one in a week that let spammers flood the service with phony promotional messages for items such as free iPhones. Last week, it was a bug in Facebook’s photo upload service that a spammer exploited to post thousands of unwanted wall messages. The newest work was found by researchers at F-Secure and Sophos, two anti-virus vendors.