The aftermath of the 2020 election put an intense spotlight on voting machines as supporters of former President Donald Trump claimed victory was stolen from him. While the theories were unproven—and many outlandish and blatantly false—election security experts say there are real concerns that need to be addressed.

In Georgia, for example, election security expert J. Alex Halderman says he’s identified “multiple severe security flaws” in the state’s touchscreen voting machines, according to a sworn declaration in a court case.