On 9 September 2026 Osmosis, a Cosmos-based exchange, said an exploit on Nomic allowed an attacker to double-spend nBTC and send false vouchers onto Osmosis. The bug, in Osmosis’s telling, sat in a custom forwarding mechanism on Nomic. Osmosis contracts and the Inter-Blockchain Communication protocol were not compromised. About 39.84 nBTC now sits inside the Alloyed BTC contract and represents about 36% of that alloy’s backing. Validators completed an emergency upgrade that Osmosis said froze 22.65 BTC in the attacker’s address. Minting, redemptions, and Nomic-related deposits are paused. Bitcoin trading in existing liquidity pools was left live, with a risk warning.
This piece is dated the morning of the statement. A full post-mortem had not shipped. Nomic had not, in the coverage we are using, posted a matching numbered account. Figures may move. Treat them as Osmosis’s operational snapshot, not a court-tested loss.
What happened
nBTC is Nomic’s bitcoin-backed asset on a Cosmos chain that runs a lock-and-mint toward Bitcoin. Alloyed BTC (allBTC) is Osmosis’s bundled bitcoin unit: a contract that holds several bridged flavours — nBTC among them — and mints one token so pools do not fragment across wrappers. Users deposit a supported variant and redeem another that still has room in the basket. If one flavour’s clipboard prints paper, the alloy’s “1:1” is only as good as the remaining honest vaults plus whatever governance does next.
Osmosis says moderation subDAOs froze inflows and outflows for Nomic and Alloyed BTC before the upgrade quarantined the 22.65 BTC. It said it would submit a seizure proposal and ask OSMO holders to let community-pool bitcoin close the remaining backing gap. No proposal ID was live with the first statement. That is a company-shaped vote on a chain, not Bitcoin miners reversing a block.
Do not mash this into Liquid’s unbacked L-BTC, Cronos’s Tectonic rewind, or Ronin’s validator keys. Different clipboards. A bridge is extra software, not a tunnel. Liquid is a Bitcoin sidechain federation. Cronos is a layer-1 that chose to rewind. Nomic is a Cosmos bitcoin bridge whose vouchers Osmosis had accepted into an alloy. Osmosis’s August pause of alloyed XRP after a different bridge incident is the in-house playbook they are repeating: freeze the alloy, keep spot pools up, wait on governance and the external chain.
Why it matters
If you hold allBTC, you hold a receipt that is supposed to be backed by a basket of receipts. A freeze on mint and redeem means you can still trade the token against whatever the pool will pay. That price is not a peg. It is a market in a damaged wrapper. If you hold bitcoin on Bitcoin, this page is someone else’s bridge. If you hold nBTC, you have a claim on Nomic’s reserve and on whether checkpoints and disbursals still work — questions Osmosis did not answer in the first post.
Phishing will impersonate Osmosis, Nomic, and “claim your backstop” sites. Nobody needs your recovery phrase to restore a 1:1. See a practical checklist for keeping crypto safer. See an exchange balance is an IOU, not a wallet if your bitcoin lives as a ticker inside a Cosmos app. See how crypto wallets actually work if the difference between a voucher and a UTXO is still mush.
What happens next
A governance vote that may or may not seize the frozen 22.65 BTC and top up the alloy; a post-mortem; whatever Nomic says about Bitcoin-side reserves and chain liveness; and pool prices that can discount the wrapper before any of that lands. Watch Osmosis’s own channels and the proposal once it has a number. We will not write this as “bitcoin was hacked”, and we will not write the seizure as done.
Not a recommendation to hold, trade, or redeem allBTC, nBTC, or OSMO. Not an instruction to buy or sell bitcoin. This incident was still unfolding when the piece was dated.
