I believe this will fix a ~14 year old bug. Browsers have been punting on dns rebinding forever. Initially documented by Collin, here are two threads:

Paper: https://crypto.stanford.edu/dns/dns-rebinding.pdf

Chrome: https://bugs.chromium.org/p/chromium/issues/detail?id=98357

Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=689835#c3