Earlier this week, Firefox 87 arrived with SmartBlock for Private Browsing — a new intelligent tracker blocking mechanism that provides stand-in scripts to decrease the chance of a website breaking on load. The list of other changes includes a new default HTTP Referrer policy, full support for VoiceOver in macOS, and more.
https://www.notebookcheck.net/Firefox-87-now-available-with-SmartBlock-as-well-as-many-minor-fixes-and-tweaks.529277.0.html