CVE-2022-29255

### Impact when a calling an external contract with no return value, the contract address could be evaluated twice. this is usually only an efficiency problem, but if evaluation of the contract address has side effects, it could result in double evaluation of the side effects. in the following example, `Foo(msg.sender).bar()` is the contract address for the following call (to `.foo()`), and could get evaluated twice ```vyper interface Foo: def foo(): nonpayable def bar() -> address: nonpayable @external def do_stuff(): Foo(Foo(msg.sender).bar()).foo() ``` ### Patches v0.3.4 ### Workarounds assign contract addresses to variables. the above example would change to ```vyper @external def do_stuff(): t: Foo = Foo(msg.sender).bar() t.foo() ``` ### References ### For more information