The newest Firefox (52.0_3) immediately segfaults on x86_64 FreeBSD 11. I've been fine for many, many versions. Just having the behavior with this latest release. firefox-esr is fine. I guess this has been going on for a week or two. Is anyone else having this issue? Thanks!
Try updating to 52.0.2,1, upstream may have fixed your crash. Otherwise, more info is needed such as FreeBSD release/version, port options selected, backtrace after a build with debugging symbols.