IndexedDB, or the Indexed Database API, is a NoSQL database technology that uses key/value pairs as records with an index over the records for high-performance queries.

“In Safari 15 on macOS, and in all browsers on iOS and iPadOS 15, the IndexedDB API is violating the same-origin policy. Every time a website interacts with a database, a new (empty) database ...

A bug in Safari in how it handles the IndexedDB API is potentially leaking information about a user's browsing habits, an issue that could be used to reveal the user's identity.