A bug has been detected on Apple’s Safari 15, that can leak your recent browsing activity and expose your Google User ID to other sites. The flaw was introduced to Safari 15 via the Indexed Database API (IndexedDB), which is part of Apple's WebKit web browser development engine, according to a Saturday blog post by FingerprintJS. IndexedDB can be utilized to save data on the computer, such as websites visited, so that they load faster when one returns.
IndexedDB likewise adheres to the same-origin principle, which prohibits websites from freely interacting with one another unless they have the same domain name (among other requirements). Imagine it being under quarantine and only being able to interact with members of your family.
Moreover, the problem discovered by FingerprintJS allows IndexedDB to break the same-origin policy, revealing data it has gathered to websites from which it did not collect it. Unfortunately, some websites, such as those in the Google network, include unique user-specific identifiers in the information sent to IndexedDB. This implies that if you're logged into your Google account, the information gathered can be utilized to accurately identify the browsing history as well as account information. It can also figure out whether you're logged into more than one account.
FingerprintJS stated, "Not only does this imply that untrusted or malicious websites can learn a user’s identity, but it also allows the linking together of multiple separate accounts used by the same user."
They also posted a video demonstrating the type of data that the attack can disclose. The flaw was reported by FingerprintJS at the end of November, but Apple has yet to patch it. All of this is alarming, but there's not much one can do about it at the moment. Because a private tab can't see what's happening in any other tabs, whether private or public, browsing in Safari's Private mode can limit the potential damage. However, it isn't without flaws.
"[I]f you visit multiple different websites within the same [private] tab, all databases these websites interact with are leaked to all subsequently visited websites," wrote FingerprintJS.
Switching from Safari to another browser can protect Mac users from the flaw, but iOS and iPadOS users are out of luck. While only Safari has been affected on Mac, Apple's requirement that both iOS and iPad web browsers utilize WebKit implies the IndexedDB flaw has affected all of these systems' browsers.