I keep getting into games where players keep getting random buffs.

In my last game a player played a 1/1 and it was suddenly a 3/3 with vigilance and nothing that he played previously or even random effects could describe.
A match a couple days ago I encountered a player that suddenly had a "player takes damage effect" and their Ajani's Pridemate started to gain life.. again and again and again... 13 times with no trigger.
In another match, suddenly the player had Hexproof on all their creatures... and I went through the graveyard and looked all the permanents abilities.