With the recent spike in the number of cyberattacks on websites using the popular web-management platform WordPress, a government-backed IT security agency urged website administrators and managers to patch a vulnerability that allows hackers to deface their sites.

The Information-technology Promotion Agency (IPA) Japan released a warning Monday, calling owners of websites that use the content-management system to update the software to the latest version "immediately" so that their websites can be protected from malevolent attacks.

More than 26 percent of websites on the internet use the open-source platform, including official websites for the Walt Disney Co., Microsoft News Center, and the Indian Prime Minister's Office, according to WordPress.