The Illinois State Board of Elections has notified voters that its online voter registration site has been hacked.

According to the letter sent to Illinois voters by the Board of Elections, “We have found no evidence that they added, changed, or deleted any information in the database. Their efforts to obtain voter signature images and voter history were unsuccessful.”

It is unclear what specific information was obtained during the hacking. The Board of Elections reported that “[T]he attackers took advantage of a programming flaw in the website’s database.” The attack, known as an ‘SQL injection’ occurs in databases using the SQL programming language.