A major bug exists in Safari 15 that can put user-privacy at risk. The IndexedDB API bug, which affects Safari users on macOS, iOS 15, and iPadOS 15, violates the same-origin policy that prevents websites accessing information from other websites that also interact with the IndexedDB database. A maliciously-designed website can thus get access to information such as browsing history and identifiers such as Google user IDs.
https://www.notebookcheck.net/Unpatched-Safari-15-bug-on-macOS-iOS-15-and-iPadOS-15-found-to-expose-browsing-history-and-Google-account-info.593271.0.html