The Berlin fork of Ropsten completed without incident on block 9812189. This fork brought changes to how the go-ethereum API handles processing of transactions. We have kept our infrastructure compatible with “unprotected” pre-EIP-155 style transactions.
EIP-155 was implemented in 2016 to prevent replay attacks across networks such as Ethereum and Ethereum Classic. Infura strives to maintain API compatibility with the go-ethereum client and prior to the Berlin fork, go-ethereum was not enforcing this compatibility check.
With go-ethereum versions 1.10.1 and up, the default behavior was changed to enforce EIP-155 compatibility. This is in the best interest of users to protect them from cross-chain replay attacks. To give our users ample time to update their applications, we will temporarily allow non-EIP-155 compliant transactions until May 17th 2021 at which point this check will be enabled across all affected networks (Mainnet, Rinkeby, Ropsten, Goerli). Please verify that your transaction signing code is updated and feel free to reach out to our support team with any questions.