The FBI and the National Security Agency warned Wednesday about the discovery of two “critical vulnerabilities” in a widely used programming language that powers websites and web applications.

The FBI's cyber division said the vulnerabilities could allow malicious actors to remotely execute code in the programming language, PHP, potentially compromising sensitive data and networks. It recommended that operators take websites offline if they can't update them immediately.

Several government and other websites were temporarily taken offline so they could be updated with security patches. The website of the Finnish government, for example, was only partly available Wednesday.…