WhatsApp has become the number one sharing app messages για κινητά, καθώς το Facebook tried to make it more than just a tool that allows users to chat from Android and iOS.
Click to Chat, for example, allows two WhatsApp accounts to communicate with each other using a QR code or a custom URL.
This feature is supposed to be used by businesses to allow their customers to communicate directly, as Click to Chat only requires a scan of a QR code to start a messaging session without even knowing the other party's phone number.
However, the phone number is revealed as soon as the conversation starts because the QR code and URLs include this information because Click to Chat could not link the two accounts otherwise.
Security researcher Athul Jayaram has discovered that this feature exposes users' phone numbers, as they could be indexed by Google because of the way QR was created.
Basically, it's all due to the metadata included in the QR code or the custom URL which, as mentioned above, includes phone numbers. WhatsApp uses a public domain called wa.me for the whole issue and once Google starts crawling the pages hosted there, it will have all the Click to Chat links created, along with the phone numbers.
Essentially, the Google can read phone numbers and then index them, enabling everyone to find out a specific phone number.
At first it may not seem like a big deal, but as the researcher explains in a analysis που he published at Threatpost, malicious users could collect a lot more information than they currently collect. For example, once a malicious user seizes someone's phone number, they can access their WhatsApp profile picture and then use the photo to search social media for more information to associate with more accounts and therefore receive additional information.
The researcher says he discovered about 300.000 WhatsApp phone numbers on Google, so he notified company owned by Facebook through a bug bounty program.
WhatsApp, on the other hand, said that the users themselves decide if they want to share any information.
“While we appreciate this researcher's report and appreciate the time he took to share it with us, it does not qualify for the bug bounty as it merely contained an engine index search with URLs that WhatsApp users have chosen to make public. All WhatsApp users, including businesses, can opt out of sharing with the click of a button," a company spokesperson said.
At the same time, Google reports that it only indexes public pages and only webmasters can remove URLs.
