PHP

PHP is a programming language used on web servers to build pages that change depending on who is visiting and what they do. If you have ever used a WordPress blog, an online shop or a forum, there is a good chance PHP was working behind the scenes. It has been around since the 1990s, which is why so many sites rely on it.

Because it is everywhere, a security flaw in PHP itself is a big deal: it can affect millions of websites at once, and the fix is usually an update that the site owner or hosting provider has to install. That is why news about PHP bugs often comes with the advice to simply apply the latest security release.