Drupal, which is a volunteer open-source project whose software is used by websites such as The White House and the Economist, said all of 7.x releases prior to 7.32 are affected, according to an advisory.
Drupal uses a database abstraction API (application programming interface) that filters harmful SQL (structure query language) queries, but the vulnerability (CVE-2014-3704) can allow an attacker to send malicious queries that could be executed. These so-called SQL injection attacks are among the most common type of attacks against a website.
"Depending on the content of the request this can lead to privilege escalation, arbitrary PHP execution or other attacks," Drupal wrote.
The flaw can be exploited by anonymous users, and there are now proof-of-concept instructions circulating that show how to exploit it, according to a FAQ document.