The Zcash developers will activate the Ironwood upgrade on July 28 at approximately 08:00 EST at block height #3,428,143. This upgrade will close the current private Orchard pool and create a new secure pool.
Ironwood addresses a vulnerability found in May within Orchard that theoretically allowed for the creation of counterfeit ZEC. When withdrawing funds from the old pool, users will undergo an account verification process, which may indicate whether the bug was exploited prior to the fix.