Facebook’s mobile app on Android has been sending user mobile numbers to Facebook’s servers over the Internet. The app apparently does this even before you sign up on the service. The privacy flaw was discovered by Symantec’s Norton Mobile Insight technology and was brought to Facebook’s attention.
The company says that hundreds of millions of people who have installed Facebook for Android are affected by the leak. Since Facebook is one of the most popular app on Android, the leak might already be widespread. Facebook replied to this development by promising an update that fixes this issue. They said that they have already deleted all such phone numbers from the servers and are not using them/processing for any use.
Facebook is a popular public company which is being used by a billion people across the world. A glitch like this can affect the privacy of so many users, especially those who expressly do not give their phone numbers. Facebook has had a very bad record with privacy flaws and once or twice a year something like this pops up to remind you that your personal information on these social networks may not be really secure. Just recently Facebook admitted that there was a bug in its contact page information storage database and they inadvertently ended up breaching the privacy of 6 million users for a period of one year. Granted that the social networking platform is complex from an engineering perspective, but they should be especially careful about stuff like contact information.
Source | Symantec Blog