Bridges are among the most attacked components in crypto, because a single contract or multisig secures a very large pot. Attacks have exploited forged deposit proofs, compromised validator keys, and upgrade functions.
The failure is visible immediately in price. When backing disappears, the wrapped-token on the destination chain depegs toward zero while the native asset is unaffected, so holders of the wrapped version take the whole loss.
Example: a bridge holding $300m is drained by forging a deposit message. Wrapped units on the destination chain, which traded at parity, collapse to a recovery estimate of perhaps 10-30 cents. Anyone using those wrapped units as liquidity-pool collateral is liquidated as well.
Related: bridge, wrapped-token