Multiple vulnerabilities were discovered in Drupal core.
Arbitrary PHP code execution
A bug in the installer code was identified that allows an attacker to re-install Drupal using an external database server under certain transient conditions. This could allow the attacker to execute arbitrary PHP code on the original server.
Information disclosure - OpenID module
For sites using the core OpenID module, an information disclosure vulnerability was identified that allows an attacker to read files on the local filesystem by attempting to log in to the site using a malicious OpenID server.
Install the latest version:
If you use Drupal 7.x, upgrade to Drupal core 7.16.
If you are unable to deploy the security release immediately, removing or blocking access to install.php is a sufficient mitigation step for the arbitrary PHP code execution vulnerability.