Mozilla Firefox Quantum v66.0.5, released on May 7, 2019, was a critical point update primarily focused on resolving a significant bug that caused browser extensions to be disabled.
Automatically prevents websites from playing sound-enabled media. Mozilla Firefox Quantum v66.0.5
Prevents web pages from "jumping" while images and advertisements load. Mozilla Firefox Quantum v66
Allows users to authenticate on websites using facial recognition or fingerprints on Windows 10. System Requirements Firefox 66.0.5 System Requirements released on May 7