It turns that the earlier claims by Gibson Security about security issues with SnapChat were not false. Now a website SnapchatDB.info has bee set up where the phone numbers and Snapchat usernames of 4.6 million people have been publicly published.
SnapchatDB has claimed that it got the data using the recently published Snapchat security exploit and that the data is being published to pressure Snapchat into improving its security.
The data published on the website is real because at least one employee of tech blog TechCrunch has found his own username and number in the published list.
If you want to know if your name is listed in the published data, you can use this website developed by Robbie Trencheny.
According to SnapchatDB, it has withheld the last two digits of the phone number to minimize abuse and spam but said that the complete data may also be released in future.