TOKYO/BEIJING — Companies and governments around the world raced on Thursday to patch newly disclosed vulnerabilities in the widely used PHP programming language, as experts reported a surge in hacking attempts following the disclosure.

The emergency response came after government websites in Europe and elsewhere went offline on Wednesday, with the disclosure sending website operators scrambling to protect their systems.

PHP developers released urgent fixes on Wednesday for vulnerabilities that had lurked in the software for years until they were uncovered using artificial intelligence, saying all users were "encouraged to update immediately." The use of AI to surface flaws that had evaded detection for years underscores the technology's expanding role in vulnerability research. PHP is a server-side language that powers a large share of the world's websites, which is why unpatched flaws in it can leave a broad cross-section of the web exposed.

Exploitation attempts escalated rapidly around the announcement. "In the 10 hours before it was publicly announced, across the network we saw thousands of attempts to exploit it," Matthew Prince, chief executive of cloud services firm Cloudflare, said in a post on social media platform X late on Wednesday. "That jumped to tens of thousands in the 45 minutes post announcement, hundreds of thousands within 2 hours, and millions now." The surge reflects a well-established pattern in cybersecurity: newly public vulnerabilities draw immediate exploitation attempts against systems that have yet to be patched.

In Japan, lender Mitsubishi UFJ Financial Group on Thursday it was temporarily suspending some internet services as part of emergency measures. Japan's Finance Ministry also suspended some website content and online services while implementing security measures. Taking services offline is a common precaution while emergency fixes are applied, and neither institution said how long the measures would remain in place.

Several governments across Asia ordered cybersecurity inspections related to the PHP flaw on Thursday. China's industry ministry urged organizations and users to immediately inspect their systems and upgrade to the latest secure version of PHP, while also recommending stronger cybersecurity monitoring and prompt changes to accounts, passwords, and keys.

South Korea's government raised its private-sector cybersecurity alert level and activated emergency response measures over the flaw, citing concerns about an increased risk of hacking attacks.

— Reuters