> Are multiple wildcards per fragment even specified?

I don't know the standard, but it sounds strange to have more than one wildcard per part of an URL. "*.*.*.google.com" looks valid to me, whereas "*a*a*a*.google.com" looks very suspicious.

Said differently, I expect:

assert max(part.count("*") for part in url.split(".")) <= 1

"*" pattern is replace with '[^.]+' regex, so I may not cause the exponential complexity issue. (I didn't check.)