Safari 15 bug can leak your recent browsing activity and personal identifiers

Illustration by Alex Castro / The Verge

A bug in Safari 15 can leak your browsing activity, and can also reveal some of the personal information attached to your Google account, according to findings from FingerprintJS, a browser fingerprinting and fraud detection service (via 9to5Mac). The vulnerability stems from an issue with Apple’s implementation of IndexedDB, an application programming interface (API) that stores data on your browser.

As explained by FingerprintJS, IndexedDB abides by the same-origin policy, which restricts one origin from interacting with data that was collected on other origins — essentially, only the website that generates data can access it. For example, if you open your email account in one tab and then open a malicious webpage in another, the same-origin policy prevents the malicious page from viewing and meddling with your email.

FingerprintJS found that Apple’s application of the IndexedDB API in Safari 15 actually violates the same-origin policy. When a website interacts with a database in Safari, FingerprintJS says that “a new (empty) database with the same name is created in all other active frames, tabs, and windows within the same browser session.”

This means other websites can see the name of other databases created on other sites, which could contain details specific to your identity. FingerprintJS notes sites that use your Google account, like YouTube, Google Calendar, and Google Keep, all generate databases with your unique Google User ID in its name. Your Google User ID allows Google to access your publicly-available information, such as your profile picture, which the Safari bug can expose to other websites.

FingerprintJS created a proof-of-concept demo you can try out if you have Safari 15 and above on your Mac, iPhone, or iPad. The demo uses the browser’s IndexedDB vulnerability to identify the sites you have open (or opened recently), and shows how the bug scrapes information from your Google User ID. It currently only detects 30 popular sites that are affected by the bug, such as include Instagram, Netflix, Twitter, Xbox, but it likely affects far more.

Unfortunately, there’s not much you can do to get around the issue, as FingerprintJS says the bug also affects Private Browsing mode on Safari. You can use a different browser on macOS, but Apple’s third-party browser engine ban on iOS means all browsers are affected. FingerprintJS reported the leak to the WebKit Bug Tracker on November 28th, but there hasn’t been an update to Safari yet. The Verge reached out to Apple with a request for comment but didn’t immediately hear back.