A cyber attack on YouTube has led to a number of offensive comments and links to adult sites appearing beneath popular videos.
The scripting attack also stopped other comments from being posted and the unpleasant ones from being deleted.
The forums on YouTube were soon inundated with complaints by users whose own videos had been targeted.
However, Google, which owns the video site, said it was quick to fix the issues.
"We took swift action to fix a cross-site scripting (XSS) vulnerability on YouTube.com that was discovered several hours ago," a spokesperson form the company said.
"Comments were temporarily hidden by default within an hour, and we released a complete fix for the issue in about two hours. Were continuing to study the vulnerability to help prevent similar issues in the future."
The main videos targeted were reportedly by teenage popstar Justin Bieber, who has become a victim of several cyber scams in recent weeks.
