Tweety bird and Porky pig

Good thing I don't use Twitter because the other day, tweeters (did I get that right?) were re-tweeting (lols makes me think of Tweety bird) spam (and Porky pig) and porn images just by hovering over tweets (how many times do I have to say tweet in this post??) due to Javascript exploits, currently the system has been patched. At least the problem was solved and no permanent damage was done. But (!) what if..users of Twitter did sustain permanent damages because of the incident, who should be liable therefor? Should it be the service provider - Twitter? News reports say that the vulnerability in the system has been discovered by a Japanese developer as early as a month ago and yet Twitter did nothing about it. It could've been worse, something vicious could have been injected in the system and the users of Twitter could've sustained heavy damage. Or should it be the seventeen (17) year old boy from Australia who decided it'll be fun to tweet an Onmouseover Javascript and caused the spamming? Well what is Onmouseover anyways? Onmouseover can actually be fun and is used by web developers to add a little interaction with their web pages, an internet article says that Onmouseover is an event handler, this means that something will happen when the mouse passes over an active text. An example would be a change in background color when your mouse passes over the text yellow. (I tried it here but it didn't work ^^') The incident may have been a prank but it could've been damaging and again it's difficult to pinpoint who is to be blamed for it because Twitter on their part was remiss as well