Security Vulnerabilities fixed in Firefox ESR 78.7 — Mozilla

If a user clicked into a specifically crafted PDF, the PDF reader could be confused into leaking cross-origin information, when said information is served as chunked data.
Using the new logical assignment operators in a JavaScript switch statement could have caused a type confusion, leading to a memory corruption and a potentially exploitable crash.
When a HTTPS page was embedded in a HTTP page, and there was a service worker registered for the former, the service worker could have intercepted the request for the secure page despite the iframe not being a secure context due to the (insecure) framing.
Performing garbage collection on re-declared JavaScript variables resulted in a user-after-poison, and a potentially exploitable crash.
Mozilla developers Alexis Beingessner, Christian Holler, Andrew McCreight, Tyson Smith, Jon Coppeard, André Bargull, Jason Kratzer, Jesse Schwartzentruber, Steve Fink, Byron Campen reported memory safety bugs present in Firefox 84 and Firefox ESR 78.6. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.