See https://www.mozilla.org/en-US/firefox/52.6.0/releasenotes/ Fixes https://www.mozilla.org/en-US/security/advisories/mfsa2018-01/ (spectre mitigations) and https://www.mozilla.org/en-US/security/advisories/mfsa2018-03/
See https://www.mozilla.org/en-US/firefox/52.6.0/releasenotes/ Fixes https://www.mozilla.org/en-US/security/advisories/mfsa2018-01/ (spectre mitigations) and https://www.mozilla.org/en-US/security/advisories/mfsa2018-03/