There definitely is an exploit, but you're phrasing it wrong. It's not a teleport, but a no clip. it's been an issue since vanilla wow and it's always remained possible but extremely detectable - go join some of those people spamming carry runs in trade chat all day, a good chunk of these are bots that will no clip their way above the map and just run to the end to pull all mobs and then AOE while being out of range.
Some higher end bots include dungeon profiles that will do this automatically.
I'm not going to be shilling and specific one, but they exist. I'd expect your account to last days if you're lucky doing something like that though - it's only viable when you're on your last leg with the account and you're ready to just suicide it until the ban hits.
