RESEARCH: In early June, @Zcash caught a soundness flaw in its Orchard shielded circuit and turned the fix into public, verifiable data. As of July 28th, the Ironwood upgrade has sealed the old pool, and formally verifies there can never be another undetectable bug in Orchard or Ironwood. As of August 10th, ~60% of all Orchard funds have migrated to Ironwood.(CoinDesk)