Twitter announced today that a bug allowed users' passwords to be stored internally without being masked. When things are working correctly, Twitter stores hashed passwords, turning them into random letters and numbers so that no one at the company can see what any user's password is. But a bug caused passwords to be stored within an internal log before the hashing process was complete. Twitter says that it spotted the problem itself and fixed it. But while it claims there has been no evidence that the passwords were misused or that they left the company's systems, Twitter is recommending that everyone change their passwords just to be safe.