Zcash rebounds a week after the fake-ZEC bug

Zcash has bounced back. A week after developers disclosed and patched a flaw in its Orchard shielded pool that could have minted undetectable counterfeit ZEC, the privacy coin rose about 19% in 24 hours to around $369 on Saturday, while Bitcoin fell 2.6%, according to data cited by Yahoo Finance as of June 6. The recovery came even after BitMEX co-founder Arthur Hayes sold his entire ZEC position. A bounce, though, is not the same as an all-clear, and the reason the bug rattled the market in the first place has not gone away.

What was the Zcash bug?

A shielded pool is the part of Zcash that hides transaction details. Instead of showing the sender, receiver, and amount on a public ledger the way Bitcoin does, Zcash can route a payment through a "shielded" address that keeps all three private. It does this with a zero-knowledge proof, a piece of cryptography that lets the network confirm a transaction is valid without seeing what is inside it. Orchard is the newest and largest of these pools, live since May 2022.

The flaw lived in that proof. It was a soundness bug, meaning the math that is supposed to confirm "this transaction is real" could be tricked into approving a fake one. In practice, an attacker could have created counterfeit ZEC inside the pool that the chain could not see or count. Because the pool is private by design, there is no cryptographic way to prove whether anyone used the bug before it was caught. That uncertainty, more than the flaw itself, is what spooked traders.

Developers moved fast. Shielded Labs, the group behind Zcash development, said the team shipped a two-phase fix: an emergency soft fork to disable Orchard transactions, then a hard fork that re-enabled the pool with a corrected circuit. The vulnerability was present from Orchard's activation in May 2022 until the emergency fix on June 1, 2026, roughly four years. Zcash's turnstile mechanism, which tracks value moving between pools, is the accounting check the team points to for confirming the total supply is intact.

For the full account of how the flaw was found and fixed, see our earlier piece, "A critical Zcash bug could have minted fake ZEC."

Why did ZEC crash after the bug was fixed?

ZEC fell from a June 4 high of $624 to an intraday low of $264.80 on June 5, a drop of more than 57%, per figures cited by Yahoo Finance. A fix was already in hand by then. So why did the price crater after the danger had passed?

The answer is the one thing the fix could not deliver: proof that nobody had already used the bug. Shielded Labs said that because of how Orchard works, there is no definitive way to tell from cryptography alone whether the flaw was ever exploited. Markets hate that kind of open question. The team assessed past exploitation as unlikely, since the bug had survived years of expert review and was caught in a deliberate white-hat effort, but unlikely is not impossible.

Hayes built his case for ZEC as a privacy bet against AI and government surveillance, then sold it for exactly that reason. He said he could not cryptographically rule out that counterfeit coins were minted in the attack window. In his words, "the privacy from AI, govt, big tech narrative demands perfection, not improbability." We covered his recent selling in "Arthur Hayes dumps HYPE and NEAR before the AI IPOs"; his ZEC exit followed the same playbook of cutting a position the moment the thesis cracked.

What drove the ZEC rebound?

A few forces lined up behind the bounce, and none of them resolves the underlying question.

A whale stepped in near the bottom. According to Lookonchain data cited by Coingape, a new wallet bought 37,316 ZEC, worth about $13.12 million, from Binance after the crash. Large buying at the lows does not vindicate the project. It is one trader's bet that the sell-off went too far.

Privacy coins also drew a bid against a weak tape. Bitcoin spent the week under pressure, with spot Bitcoin ETFs recording a net outflow of $326 million on Friday, per SoSoValue data cited by Yahoo Finance. ZEC's relative strength stood out precisely because the majors were sliding.

Then there were the backers. Gemini co-founder Cameron Winklevoss framed the discovery as proof the project's security process works, calling it "a vote of confidence, not a cause for alarm." Others noted this is not new territory for privacy coins: Nic Carter of Castle Island Ventures pointed to a Zcash bug found in 2018 and a Monero flaw from 2017, both of which theoretically allowed counterfeit coins before they were fixed. "It's basically part of the deal," he told Decrypt.

How did AI help find the bug?

One detail is drawing as much attention as the bug. The flaw was surfaced with the help of an AI model. Security researcher Taylor Hornby found it during an audit for Shielded Labs, working with Anthropic's Claude Opus 4.8, according to disclosure details reported by Decrypt and other outlets. The flaw had survived years of human review before AI assistance helped uncover it.

Outlets are framing Zcash as the latest example of AI turning up vulnerabilities that survived years of human review. Decrypt reported that researchers are increasingly using frontier models to find software flaws, and quoted security professionals warning the same tools will reach attackers, not just defenders. Stanislav Fort, a former DeepMind and Anthropic researcher now running the security firm Aisle, argued the fix is not to lock these tools away but to get them into defenders' hands, since "the capability for zero-day discovery is already widely distributed across models that no one can restrict."

The crypto stakes are concrete. Decrypt, citing the same reporting, noted more than $840 million was stolen from DeFi projects in the first five months of 2026. Code that is public and holds money is a standing target, and AI lowers the cost of probing it from either side.

Does the bounce mean the scare was overblown?

A bounce settles the chart, not the question. The bug is patched and the turnstile accounting is the basis for the team's claim that the total supply is intact, which is the system working as it should: a flaw caught by a white-hat, disclosed, and fixed in days rather than months. That is genuinely the good outcome.

But the thing a shielded chain is built to prevent is a silent counterfeit, and this bug was exactly that. Privacy cuts both ways. The same design that hides a legitimate user's payment also hides whether anyone abused the flaw before it was closed. No price recovery changes that, and "we think it's unlikely" is the strongest answer the math allows.

What we're watching

Shielded Labs has floated a network upgrade meant to close the open question for good: a replacement shielded pool with turnstile accounting that would force existing Orchard coins through a new, verifiable checkpoint, so anyone could publicly confirm the supply with no counterfeit ZEC inside. The team has also said it will keep working with Hornby on AI-assisted security and pursue formal verification of the Orchard circuit.

The real test is whether the next round of audits, AI-assisted or not, catches the next flaw before someone with worse intentions does. ZEC reclaiming its old price is beside the point.