MetaMask has launched Added Protection, a new security feature designed to close a long-standing vulnerability in how self-custody wallets handle transaction previews. The feature targets so-called "red pill attacks," a phishing scheme in which a malicious smart contract detects that it is being simulated and behaves innocently during the preview stage, displaying a clean, expected outcome such as a small incoming transfer, only to carry out entirely different, often malicious behavior once the user signs. In practice, Added Protection embeds the simulated outcome of a transaction into its execution requirements, so a signed transaction reverts if its real behavior deviates from the preview shown to the user.

The mechanics of the attack exploit a structural gap that persists across most crypto wallets. Before a user approves a transaction on an application, the wallet displays a simulated preview of what is supposed to happen. These previews exist because raw transaction data is largely unreadable to non-technical users, so wallets run the intended operation against the blockchain's current state and translate the result into a human-readable summary before anything is broadcast. Historically, this preview has been purely informational: nothing has enforced a match between the simulated result and the actual on-chain execution. A sophisticated attacker can therefore write a contract that returns benign data during simulation but drains the user's funds or transfers assets elsewhere when the real transaction runs. Because the preview appears legitimate, victims have no reason to hesitate before signing.

Announcing the feature on X on September 17, 2026, MetaMask wrote:

MetaMask is the first self-custody wallet that stops red pill attacks. The scam: a transaction looks safe in the preview, then drains your wallet after sign. Added Protection ensures what you see is what happens. If it doesn't match, it reverts. Your funds stay put.… pic.twitter.com/N7FeXjGGOg

— MetaMask (@MetaMask) September 17, 2026

Locking the Preview Into the Transaction

Added Protection addresses the gap by converting the preview from a mere estimate into a binding condition. When a user initiates a transaction through an app, MetaMask simulates it and presents the expected result as usual. The key difference is that the simulated outcome is now embedded into the transaction's execution requirements. If the real execution deviates from what was shown — the signature behavior of a red pill contract — the transaction reverts automatically and the funds never leave the wallet.

Users should be aware of one caveat: even when a transaction fails under this mechanism, the network gas fee for the attempted execution is still consumed. On Ethereum and comparable EVM chains, a reversion cancels the transaction's state changes while still compensating the network for the computation already performed, which is why the fee applies even when the transfer itself is blocked. MetaMask itself charges nothing for the feature and takes no fee on reverted transactions. The company also notes that the protection guards against deliberately manipulated outcomes, not ordinary market movements or slippage caused by legitimate price changes.

The feature reflects a broader design philosophy of preserving user autonomy. MetaMask does block transactions users intend to make; it only guarantees that the transaction approved on an Ethereum or EVM application is the transaction that actually runs. Added Protection is enabled by default but can be switched off directly on the confirmation screen, leaving risk management in the user's hands.

MetaMask positions itself as the first self-custody wallet to offer this guarantee. The feature is currently live in the MetaMask browser extension version 13.45, covering 13 EVM networks that support Smart Accounts under the EIP-7702 standard, which allows conventional externally owned accounts to take on smart-account capabilities. Mobile support is expected to follow in a later release.

The stakes of this gap are structural: in self-custody, no intermediary can reverse or refund a signed transfer, so the signing step concentrates the bulk of the security burden on individual users. Because red pill attacks are particularly effective against users approving large transactions or interacting with unfamiliar contracts, the feature is likely to become a meaningful baseline safeguard for the growing number of users transacting with decentralized applications.

Source: Metaverse Post