branch.io bug left '685 million' netizens open to website hacks

That staggering nine-figure number is because the security issue was actually within a toolkit, called branch.io, that tracks website and app users to figure out where they've come from, be it Facebook, email links, Twitter, etc.

Among the sites found to be using the vulnerable components were reviews site Yelp, cash wiring biz Western Union, Shopify, and photo-sharing site Imgur, it is claimed. Hochstadt estimated the sites together handle around 685 million user accounts.