"While the vendor has fixed many of these flaws, many important vulnerabilities remain unaddressed," the report said.

The lab found, for example, that someone with only brief access to a machine could replace a memory card with one preprogramed to read one candidate's votes as counting for another, essentially switching the candidates and showing the loser winning in that precinct.

"The attack can be carried out with a reasonably low probability of detection assuming that audits with paper ballots are infrequent," the report said.

Browning asked Diebold Elections Systems to address the problems by Aug. 17, and expressed confidence that the company will do so before next year's primary election.

"To Diebold's credit, they have come to the table and been willing to get these changes made and get them made timely," Browning said.

A company spokesman said the deadline would be met.

"These are not major changes, and we are confident we can meet the deadline," said Mark Radke, who also said the company has worked well with the state. "We look forward to continuing this relationship and to continuing to improve the security of our elections systems."

Browning said that the memory cards are locked in machines and that only a few people have access to them in a setting where others wouldn't see them unscrewing machines, breaking seals and switching cards.

"It is not where you just walk up to a machine and pop out a card," he said.

Tampering with the software is much easier in a laboratory than trying to carry out the same actions during an election, Browning said. Still, he said, his office will advise county elections supervisors on steps that should be taken to ensure machines won't be tampered with.

Florida's voting system drew national attention in 2000, when dimpled, pregnant and hanging chads on punch card ballots held up a final count in the presidential election. Florida was eventually decided by 537 votes after the U.S. Supreme Court stepped in, handing the election to George W. Bush. The state has since banned the punch cards.

Currently, 15 of Florida's 67 counties use paperless touch-screen voting machines, while the rest use optical scan machines where a voter marks a paper ballot with a pencil and it is electronically scanned. Touch-screen machines are being scrapped because of a newly signed state law that requires a verifiable paper trail for all voting machines.