Security vulnerabilities fixed in Firefox ESR 52.5 — Mozilla

A use-after-free vulnerability can occur when flushing and resizing layout because the PressShell object has been freed while still in use. This results in a potentially exploitable crash during these operations.
The Resource Timing API incorrectly revealed navigations in cross-origin iframes. This is a same-origin policy violation and could allow for data theft of URLs loaded by users.
Mozilla developers and community members Christian Holler, David Keeler, Jon Coppeard, Julien Cristau, Jan de Mooij, Jason Kratzer, Philipp, Nicholas Nethercote, Oriol Brufau, André Bargull, Bob Clary, Jet Villegas, Randell Jesup, Tyson Smith, Gary Kwong, and Ryan VanderMeulen reported memory safety bugs present in Firefox 56 and Firefox ESR 52.4. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code.