Emergency Action Restricts New Activations
The Arbitrum Security Council temporarily blocked new Stylus contract activations on Arbitrum One and Nova in an October 2 emergency action. The restriction applies to programs and app updates that require fresh activation.
Arbitrum attributed the precaution to increasingly sophisticated AI-assisted attacks involving hand-crafted WebAssembly programs outside the standard Stylus compiler toolchain. The Council noted that known Stylus bugs primarily threaten chain liveness, including denial-of-service risks, and stated that no attack permitting the theft of user funds has been discovered.
The restriction was implemented by raising the activation gas requirement to a prohibitively expensive level, a configuration change that required no upgrade to the network's ArbOS operating software.
Impact on Developers and Existing Contracts
Ordinary Solidity contract deployment and execution remain entirely unaffected by the emergency action. Furthermore, already-active Stylus applications can continue running until their expiration.
Developers can still extend an active program's lifetime using the permissionless keepalive renewal mechanism before it expires. However, new application versions requiring fresh activation cannot become executable, and the reactivation of an already-expired program is blocked.
New contract instances that use identical program code can reuse an existing activation as long as it remains valid. The official notice did not provide a specific date for reopening activations, stating that the Arbitrum Foundation will work with ArbitrumDAO on the timeline and manner of restoration.
New Safeguard for BoLD Withdrawals
Alongside the Stylus restriction, the emergency action installed a separate safeguard for BoLD's one-step proofs on Arbitrum One. Under this safeguard, anyone can present two conflicting answers to the same step of an open challenge.
If the one-step proof accepts both conflicting answers, a guard puts Arbitrum One's settlement to Ethereum on hold. While the chain would continue processing normally during such a suspension, unconfirmed messages and withdrawals from Arbitrum One to Ethereum would be delayed until the Council deploys a fix and resumes settlement.
