PHP sits underneath popular web design platforms, so the weaknesses potentially affect a vast range of websites, from online stores and news outlets to government services.
Wiz, one of the security firms that found the flaws, estimated that PHP runs about 70 percent of the world’s websites and said they rank “among the most severe vulnerabilities discovered in PHP, and arguably in software history.”
The US National Security Agency told organisations to patch immediately or pull vulnerable systems offline.
Only sites that run PHP on their own servers are exposed.
Many large platforms are built on other programming languages or use operators that could install the fix quickly and were able to stay online.
The flaws “often provide a direct path to the server’s file system or database,” the NSA said in a statement on X.
Attackers could use them to take over web servers without needing a password.
Volker Dusch, a security engineer at the PHP Foundation, told the Wall Street Journal it was the most serious problem PHP had faced in more than a decade, comparing it to Heartbleed, a 2014 flaw that set off a worldwide rush to patch.
The discovery came amid a surge in software security disclosures driven by increasingly powerful AI models, with the number of vulnerabilities found in 2026 on track to roughly double last year’s record total.
PHP programmers released a fix on Wednesday.
“If you run PHP, it is imperative that you update now,” the PHP Foundation, which funds developers working on the language, said in a blog post.
Security firm Calif found the flaws in August using OpenAI’s GPT-5.6 Sol model, as part of an OpenAI-funded audit of PHP’s code.
Wiz, which is owned by Google, said it found them independently weeks later with help from AI models including Google’s Gemini 4 Argon and GPT-5.6 Sol.
OpenAI said on X that it considered the flaws “one of the most impactful vulnerabilities in recent memory,” adding that the discovery “marks a new phase, where AI can find security bugs with internet-scale impact.”
The flaws had been reported privately to PHP’s developers and kept confidential while a fix was prepared.
Details leaked online on Tuesday, a day before the planned release of the fix, prompting the rush to take sites offline before hackers could exploit them.
In France, local government websites, including one for the Paris police, were made inaccessible at the request of the French National Cybersecurity Agency, the interior ministry said.
In the Netherlands, the national digital identity service DigiD, the website of the House of Representatives and the site of the national cybersecurity centre went offline as a precaution, according to Dutch public broadcaster NOS.
In Australia, the Australian Signals Directorate said its own cyber.gov.au site was among government websites affected by the flaws, according to Australian public broadcaster ABC.
The Wikimedia Foundation, which runs Wikipedia, warned users they could see outages on its sites while it addressed the flaws, and said it had deliberately taken many of its supporting services offline until they could be safely patched.
Several Pokemon apps, including Pokemon HOME, Pokemon Champions and Pokemon Sleep, also went offline on Wednesday for emergency maintenance, with Pokemon Sleep citing security measures, according to gaming news site Kotaku.
The operator of the hit Japanese game Umamusume said it was carrying out maintenance to fix a PHP vulnerability found in its servers. (AFP)