mIRC does not recognize URLs with literal IPv6 addresses like http://[2a00:1450:4016:800::1012]/ anymore. This works on 7.19, but doesn't in 7.25 and 7.26 - I guess 7.23 broke it.

I can confirm this behavior.

However, it has nothing to do with IPv6. mIRC is actually stopping at the [.

For example double clicking "http://www.example.com/test[foobar]" (which is a perfectly fine URL (just unencoded)) opens "http://www.example.com/test".

[] should normally be encoded.

This is related to https://forums.mirc.com/ubbthreads.php/topics/238811/mIRC_can_t_handle_URLs_properl

IPv6 might need a special exception. It's well defined enough to not interfere with the current punctuation delimiters.