Government websites in Europe and elsewhere went offline on Wednesday after the disclosure of critical vulnerabilities in a widely used programming language sent website operators scrambling to protect their systems.
Developers of the PHP programming language said Tuesday they had identified two critical vulnerabilities and urged users to update their sites as soon as a fix was released. They said around 1345 GMT on Wednesday that a new version fixing the vulnerabilities was live.
But with reports that hackers were exploiting the flaws to break into websites, government agencies in the Netherlands and Finland were among those that took sites offline ahead of the fix as a precaution.
PHP underpins large parts of the internet, raising concerns that a significant number of websites could be vulnerable to attack.
"PHP is everywhere. It quietly powers WordPress, Drupal, Joomla, and Magento sites, shared hosting platforms, control panels, and an awful lot of software that doesn't even advertise that it runs PHP under the hood," cybersecurity company Huntress said in a blog post.
Dane Knecht, the chief technology officer of Web and cloud security firm Cloudflare, said that attacks were emerging and Cloudflare was updating its firewall rules as a stopgap measure.
"We are seeing early attacks emerging and are updating mitigations as new vectors show up. This is a STOPGAP only. Patch as soon as PHP releases the update," he said on X.
Wordfence, a security plugin that protects WordPress websites, said all WordPress sites run on a PHP-installed server. It warned that automatic updates would not apply the fix and advised site owners to find out who is responsible for updating PHP on their sites.
Cybersecurity agencies in Europe, Australia, Japan and Britain have urged PHP users to update immediately or take websites offline until patches can be applied. The Dutch cybersecurity agency itself went offline, saying it had done so as a precaution because of the vulnerabilities.
Officials have said that all PHP versions from PHP 5 onward could be affected, although PHP has not yet disclosed which versions are vulnerable.
Critical Software
PHP is a programming language used to run websites. When a visitor loads a page, a server running PHP assembles the content and sends it to the browser. It is free, open-source software maintained by volunteers.
It is also among the most widely used software on the internet. PHP runs roughly 75 percent of websites whose programming language can be identified, according to web technology tracker W3Techs. It is the engine behind WordPress, which powers about 43 percent of all websites from blogs and small business pages to government portals, online stores and news sites.
Automattic, the company behind WordPress.com, said: "We don't comment on the details of security issues, but our team is prepared and has been working with the PHP security team to ensure a smooth update."
Security experts said the vulnerabilities could potentially open the door to millions of servers because so many websites rely on the same underlying software. Rather than target victims individually, attackers could scan the internet for systems running vulnerable versions of PHP.
AI-assisted hacking campaigns, which have proliferated in recent weeks, could magnify the threat, said Lukasz Olejnik, a visiting senior research fellow at King's College London.
"The scale is huge," Olejnik said. "And with AI exploitation may happen instantly, on a large scale."
The risk is particularly acute for small websites run by individuals or organisations with limited technical resources, often on shared hosting services where customers do not directly manage the underlying servers. Security experts said such sites could take longer to patch and remain exposed well after fixes become available.
Mass Outages
In the Netherlands, several organisations followed the example of the National Cyber Security Center and took public-facing websites offline, including the Port of Rotterdam, government portal, the national soccer association KNVB, the websites of the country's five largest political parties and several hospital websites.
Danish municipal IT company Kombit said it had shut down several services, including the national school communication platform, a spokesperson told Reuters.
Disruption was even more widespread in Finland, where state IT services provider Valtori said government public network services had been taken offline "as a precautionary measure".
France's Interior Ministry said it had temporarily taken local government administrative websites offline while awaiting a security fix.
The US cybersecurity agency CISA did not respond to emails seeking comment.