After it was recently revealed that top Facebook applications leaked user IDs to advertising companies, some of MySpace's third-party developers were caught doing the same thing.
On Monday, the Wall Street Journal (WSJ) broke the news that many Facebook applications, including all in the top ten, were passing user IDs (UIDs) to other parties via referrer URLs.
UIDs are unique numbers, which identify Facebook users and can be used to easily access their respective profiles.
Because Facebook instructs people to use their real name, the leak can enable advertisers to associate ad clicks with individual persons and this can have serious consequences to their privacy.
Both Facebook and MySpace had the same problem themselves back in May and corrected it after it was reported in the media.
However, according to a new WSJ article, just like Facebook's applications, some of MySpace's were also found to be in violation of the network's terms of service earlier this week.
The offending apps included TagMe, with 8.3 million users, RockYou Pets, with 6.1 million, and GreenSpot, with 1.8 million.
"It has recently come to our attention that several third-party app developers may have violated these terms and we are taking appropriate action against those developers," a MySpace representative said.
It seems the exposure might be more limited in this latest case, because unlike Facebook, MySpace allows people to use aliases instead of their real names.
The breach is likely to be accidental and the leaking of sensitive information via referrer URLs is a Web-wide problem.
Spokespersons for both RockYou and BitRhymes, the creator of TagMe, told WSJ that the problem was corrected as soon as the companies learned of it.
But, if past experience is any indication, they might be the target of some class action lawsuits soon. Zynga, the largest developer on Facebook has been days after the breach was reported.