During one of the Ranked Match game, a player (Pudge) from team Radiant managed to hack Dota 2 server and spawned unlimited heroes at Fountain. He then gained 35k HP and max levels by killing those dummy Level 1 heroes and getting the strength points using 3rd skill Flesh Heap. The allies were also receiving experience points. The Pudge became too strong, he was able to 1 hit K.O all the heroes in Dire team. Here are some screenshots from that game. The Match ID is 449960886, in case if you want to watch the replay.
It seems that Dota 2 is still vulnerable to hacks and other exploits. Valve needs to act and fix these exploits in the next update or they might get misused by cheaters. There are several other cases where players reported Dota 2 maphack and gold hack use.