Hackers have targeted Justin Bieber videos on YouTube, exploiting a cross-site scripting vulnerability which enabled them to bombard viewers with pop-up messages and redirect them to porn sites. The hack attack lasted for the best part of two hours before Google was able to isolate the problem and apply a fix.

As well as using Justin Bieber video clips as the bait for the attack, the hackers also took the opportunity to leave abusive and obscene comments about the popular teen idol singer. A number of banner messages even appeared beneath the most popular Bieber videos proclaiming that he was dead. A Google spokesman told The Telegraph that the YouTube hack had been dealt with swiftly , claiming "Comments were temporarily hidden by default within an hour, and we released a complete fix for the issue in about two hours. We’re continuing to study the vulnerability to help prevent similar issues in the future."

Meanwhile, security expert Graham Cluley points out that this is a big target with millions of visitors a day and hopes that YouTube will be investigating what went wrong with their processes , as well as "explore if they are reviewing code properly before it is made live to ensure that loopholes aren't left in their code in future."

This isn't the first time that Justin Bieber has found himself at the centre of an online controversy. DaniWeb has previously reported how Twitter tweaked its trending algorithm to prevent Justin Bieber being at the top all the time, and a service which took delight in removing all traces of Bieber also courted controversy.