Popular apps aimed at children may be collecting their personal data and sharing it without their parents' permission, according to the Federal Trade Commission.
FTC researchers tested 400 of the leading smart phone and tablet apps sold in stores run by Apple and Google.
The study concluded the software developers offered misleading privacy policies.
"We're not naming names, in part because we think this is a systematic problem, and we don't want people to think that if they avoid certain apps that they're home free," Jessica Rich, associate director of the FTC's financial practices division, said.
The news comes as the FTC prepares to vote on new rules to keep companies from tracking children on mobile devices.
Current laws limit advertising to children in print and television, but it is not as clear for mobile technology.