In Vanilla and Burning Crusade, Corrupted Ashbringer was never obtainable. It was in the game files, but there was no way to craft it, loot it, or otherwise get it to drop.
We had mod items come into the possession of players during that time. Never Corrupted Ashbringer. Why do you think there's a gray book on how to fish it up with most of it's pages missing ingame? It's an easter egg to that.