TweetDeck, Twitters tool for managing the influx of and sending of 140-character messages, has been hit by an XSS (cross-site scripting) attack that caused warning dialogs to pop up and prevented usage of the client.Cross-site scripting is a type of injection with malicious content that can be carried out on a web application that uses input from an attacker without validating the code. But in some cases the problem was more serious than this as messages (some of them obscene) from unk…