Syscoin pauses bridge after hack mints 5 billion SYS

The Syscoin blockchain project has temporarily suspended its crosschain bridge after an attacker exploited a validation flaw to mint approximately 5 billion unauthorized SYS tokens, an incident that sent the token's price tumbling nearly 20 percent. The exploit, disclosed by the Syscoin team in a preliminary postmortem on June 7, created an illicit output valued at just under $10 million at the time.

According to the project's investigation, the attacker abused a weakness in the bridge's relay path, which incorrectly accepted a fraudulent transaction proof. This caused the system to treat the submission as legitimate and mint the tokens on Syscoin's UTXO chain, a foundational layer of its dual-chain architecture. The funds were initially sent to a single address before being split across two wallets, one holding roughly 4 billion SYS and the other holding about 1 billion.

In response, the Syscoin team immediately paused the bridge and has advised users not to interact with it until further notice. The project said it has identified the affected validation path and prepared a fix, which is now undergoing security review and implementation. A key part of the containment strategy...