Mozilla retires Firefox 4 from security support
This is especially noteworthy for those who never actually close their browser and would thus not receive the upgrade notice.
That's because Firefox 4 has reached what Mozilla calls EOL, for "end of life," for vulnerability patches.
Although the move may have caught users by surprise, the decision to stop supporting Firefox 4 with security updates has been discussed by Mozilla's developers and managers for weeks.
A mozilla.dev.planning mailing list thread that started May 17 evolved into a back-and-forth about the rapid-release schedule and its impact on Firefox 4.
Christian Legnitto, the Firefox release manager, put it most succinctly in a May 25 message. "Firefox 5 will be the security update for Firefox 4," Legnitto said.
This is especially noteworthy for those who never actually close their browser and would thus not receive the upgrade notice.