The two states have used the systems for five years, allowing voters to register to vote and log in to update their address information online. The information needed to access voters' accounts is publicly available, The New York Times reported Saturday.
The Times said it was able to track down the information needed to update the accounts of several prominent executives in Washington state in about 3 minutes.
Security experts told the Times computer hackers could write a few lines of code to change an address or party affiliation instantly for thousands of voters at once. This is a concern in Washington state, where residents vote entirely by mail-in ballots.
Ross Goldstein, the deputy administrator of the Maryland State Board of Elections, said address changes require a confirmation letter to be sent to a new address. The system also requires changes to be verified by captchas -- online puzzles meant to decipher between humans and computers.
"What is technically possible and what realistically could happen are very different," Goldstein said.