Arbitrum Halts New Stylus Activations Amid AI-Assisted Attack Concerns

Arbitrum has temporarily halted new Stylus contract activations on its Arbitrum One and Nova networks following AI-assisted attacks that could compromise chain availability. The emergency measure, implemented by the Arbitrum Security Council on October 2, 2026, prevents new Stylus contracts from being activated but does not affect existing contracts or users interacting with deployed applications.

The issue arises from AI-assisted development tools making it easier to create sophisticated attacks against hand-crafted WebAssembly programs. This has raised concerns about the potential for network performance degradation and impact on other users. However, Arbitrum has assured that no attacks have been identified that could enable the theft of user funds.

The restriction on new Stylus activations is focused on deployment rather than execution, allowing existing contracts to continue running and users to interact with them as usual. The ArbOS 61 upgrade ensured that none of the active Stylus contracts on Arbitrum One would expire before August 20, 2027, but reactivating a contract after expiration or deploying an updated version remains subject to the pause.

Arbitrum has implemented an additional safeguard for its one-step proof mechanism under BoLD, which validates the chain's state before it is settled to Ethereum. The new OspSoundnessGuard can pause settlement between Arbitrum One and Ethereum if conflicting proof is accepted, providing a precautionary measure to prevent potential issues.