Hackers have posted what they say are usernames and partial phone numbers of 4-point-6 million users of mobile photo-sharing service Snapchat.
A group says it published the data on a website in an effort to convince makers of the app to beef up its security.
Snapchat, which allows people to send photos or video snippets timed to self-destruct 10 seconds or less after being opened, has become hugely popular among teenagers who are easing away from Facebook.
But Australian firm Gibson Security warned last week that glitches in the application could be exploited by hackers.
"Our motivation behind the release was to raise the public awareness around the issue," the hackers said in a statement, published on TechCrunch late yesterday.
"It is understandable that tech startups have limited resources but security and privacy should not be a secondary goal. Security matters as much as user experience does.
"You wouldn't want to eat at a restaurant that spends millions on decoration, but barely anything on cleanliness."
Created by students at Stanford University in 2011, Snapchat reportedly rejected a $3 billion takeover offer from Facebook last year.
Conor Flynn is Managing Director of ISAS and an information security expert- he spoke to Sinead Spain
