I'm no longer able to log into my bank (www.kbc.be). Trying to provide STR is probably useless due to it requiring several security keys, but I bisected the problem to: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=1053bf2fbaed195d37a07ae81d5086cac0b8f6b8&tochange=abcd8dfc3a869a1c5292f91b48b7e21f48766f59
Hi :gcp, as bug 1405571 was backed out from m-c, is this issue still reproducible for you? https://bugzilla.mozilla.org/show_bug.cgi?id=1405571#c24
Fixed in current Nightly.