It’s possible to bring a buff from Legion that gives 10% to all stats into M+, while it only lasts for 5 minutes it’s enough to help with the initial pull and a couple of packs before the buff falls off.
Currently there are players in China and Taiwan that are abusing this buff and more to achieve title range when without them they couldn’t pass 15’s.
If possible a solution that can future proof abuse in M+, is make it so that when inserting a key in M+ it checks all abilities and spells in your spell book and clears any buffs that are not in said spell book.
Side note, there are players in Taiwan that abused the dreamsurge buff last season that didn’t get their title striped, please look into it.
Edit (June 07) :
They’re still abusing and bringing various buffs into M+ to complete high key levels.
Empowered Globule (NPC ID 103502), when killed drops a Condensed Energy (object ID 247415), and gives the buff Empowered Slime (spell ID 204856) when used.
Said buff among others buffs they’re abusing doesn’t show up in the logs even when uploaded to WCL.