Arbitrum Pauses New Stylus Contract Activations After Emergency Upgrade

Arbitrum’s Security Council carried out an emergency upgrade on Arbitrum One and Nova at 11:30 a.m. U.S. Eastern Time on October 2, pausing all new Stylus contract activations on both chains and adding a new safeguard for BoLD single-step proofs in Arbitrum One’s dispute system. According to ChainCatcher, Arbitrum Foundation said the move is part of ongoing proactive security measures intended to protect the network’s security and integrity.Stylus lets developers write smart contracts in Rust, C++, and other languages while remaining compatible with the Ethereum Virtual Machine, with programs compiled into WebAssembly. The pause mainly targets manually written WASM programs that do not use the standard Stylus compiler toolchain and have not yet been patched by the current version of ArbOS. The Security Council raised the gas required for activation to the theoretical maximum by calling ArbOwner.setWasmActivationGas(2^64 - 1), making new activations economically impractical.Already activated Stylus contracts are not affected and can continue to run and renew, while Solidity contract deployment and execution remain unrestricted. The new BoLD safeguard allows anyone to pause settlement from Arbitrum One to Ethereum if two conflicting but accepted answers appear in the same dispute step, which could delay unconfirmed withdrawals while the Security Council deploys a fix. Officials said the Stylus-related vulnerabilities identified so far mainly affect chain liveness, such as denial-of-service attacks, and do not threaten user funds.