Firefox 53.0.3
https://www.mozilla.org/en-US/firefox/53.0.3/releasenotes/
Fixed
Fix excessive resource usage from the captive portal detection service (bug 1359697)
FIx hangs when using a proxy with NTLM authentication (bug 1360574)
Changed
Bump preloaded security information expiration times (bug 1364240)
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Now available via the program's internal updater: Help / About Firefox