Firefox ESR 52, slated to ship on March 7, will be what Mozilla moves XP and Vista users to.
Mozilla created the ESR track in 2012 after some customers balked at its scheme to ship a new edition of the browser every six weeks.
(Microsoft adopted a similar approach with its Windows 10 Long Term Servicing (LTS) Branch, a release track that eschews feature changes for months, or even years.) Instead, Firefox ESR remains feature-static for approximately a year, at which time a new ESR is issued. ESR builds are regularly updated with security fixes, but do not receive the new features and enhancements that the standard version does.
