Хитрожопый Firefox.
Нужно найти файл Program Files\Mozilla Firefox\greprefs\all.js

В нем дописать в конце строчку

pref("network.security.ports.banned.override", "87");

all.js

// If there is ever a security firedrill that requires
// us to block certian ports global, this is the pref
// to use. Is is a comma delimited list of port numbers
// for example:
// pref("network.security.ports.banned", "1,2,3,4,5");
// prevents necko connecting to ports 1-5 unless the protocol
// overrides.