British classifieds site Gumtree.com suffered a data leak after a security researcher revealed that he could access sensitive personally identifiable data of advertisers simply by pressing F12 on the keyboard.
When pressing the F12 key in a web browser, the application will open the developer tools console, which allows you to view a website’s source code, monitor network requests, and view error messages produced by the website.
It is considered a primary security measure to make sensitive data not publicly viewable when using a website, even if you view its source code.
However, Pen Test Partners security researcher Alan Monie discovered that he could see the PII of sellers simply by viewing the HTML source code of the advertising shown on Gumtree’s website.
“The site was super leaky. Every advert on the site included the seller’s postcode or GPS coordinates – even if the seller requested the map of their location to be hidden. It leaked the sellers email address, and their full name was available via a simple IDOR vulnerability,” explained a report by Monie.
Gumtree is one of the top 30 websites in the UK, receiving many millions of unique visitors every month. As such, this leak may have impacted a large number of advertisers on the site.