Security researchers say bug may have affected nearly 100,000 Facebook applications for years. Certain applications inadvertently gave advertisers access tokens to access Facebook accounts. Facebook has fixed the bug, but it could still be a big problem for users, researchers say. Users should change their Facebook passwords, like “changing the lock” on their account, they say. Facebook representatives could not immediately be reached for comment on the issue. It’s not clear whether anyone realized that this problem existed, so it’s possible that nobody has taken advantage of it.”]