Spiders spawn even after putting torches on spawner in survival mode

Issue: Spiders spawn even after putting torches on the spawner itself.

What I expected to happen: I expected spiders to stop spawning once I found their spawner and marked it with torches.

What really happened: I found the spider spawner after seeing water dripping above me in game. I followed the water up to see where it lead to. It lead directly to the spider spawner that I had been hearing while playing normally. I then marked the spawner by placing torches on it expecting it to stop spawning spiders. I played for a little while longer around the area and spiders kept spawning from the spawner that had torches directly on the sides and top of it. From watching YouTube videos I knew this was a bug that wasn't supposed to be in the game. I will check if this is the case in Pocket edition as well or not. If so I will confirm it by adding a comment below with the version I am playing on my phone.