Comment

Author: ernestognw

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Bug fixes
 
 - `ERC165Checker`: Ensure the `supportsERC165` function returns false if the target reverts during the `supportsInterface(0xffffffff)` call. ([#5810](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/5880))
+- `AccountERC7579`: Prevent revert in `isModuleInstalled` for fallback modules when `additionalContext` has fewer than 4 bytes. The function now returns `false` instead of reverting, ensuring ERC-7579 compliance. ([#5961](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/5961))
 
 ### Breaking changes
 

contracts/account/extensions/draft-AccountERC7579.sol

@@ -150,6 +150,7 @@ abstract contract AccountERC7579 is Account, IERC1271, IERC7579Execution, IERC75
         if (moduleTypeId == MODULE_TYPE_VALIDATOR) return _validators.contains(module);
         if (moduleTypeId == MODULE_TYPE_EXECUTOR) return _executors.contains(module);
         if (moduleTypeId == MODULE_TYPE_FALLBACK)
+            // ERC-7579 requires this function to return bool, never revert. Check length to avoid out-of-bounds access.
             return additionalContext.length > 3 && _fallbacks[bytes4(additionalContext[0:4])] == module;
         return false;
     }