What is PHP, and how bad is the computer language flaw causing website shutdowns globally?

Automated excerpt

Websites across the world have been taken offline in the past day as governments and businesses work to patch newly discovered vulnerabilities in PHP, a programming language that underpins much of the internet. Content management systems and publishing template systems such as Wordpress are built on PHP. An estimated 70% of websites use PHP, with millions of sites potentially affected by the vulnerabilities. But according to the PHP Foundation, it discovered the two vulnerabilities had begun circulating on forums and social media on Tuesday (UTC time), and so brought forward the disclosure. How bad is it? Bad.

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