Backlog Controlling an opponents Mystic Forge lets you see the top card of their library

[EastTM]

Gained control of an opponents Mystic Forge with the effect of Dack Fayden. During the damage step the box showing my top card with Mystic Forge would change to a different card. I cant be 100% sure it was my opponents top card, but it wasnt my top card or any card in my deck, and two out of three cards that were shown were played by my opponent the following turn. This happened three times, and each time i was attacking with a creature so attacking might be required to recreate the bug.

 

[ManaDrainThis]

This is a broader bug that impacts several cards which allow their controller to view and potentially play the top card of their library. Is confirmed to impact a stolen Bolas’s Citadel and Augur of Autumn, as well as Mystic Forge.

https://forums.mtgo.com/index.php?threads/controlling-opponents-augur-of-autumn-allows-me-to-see-top-of-opponents-deck-during-combat.1047/