Government websites in Japan, including the National Tax Agency’s online tax filing system, have been temporarily taken offline as a precaution following the discovery of a critical security vulnerability in the PHP programming language.

The National Tax Agency suspended access to its e-Tax website, which allows taxpayers to file returns and make tax payments online, on October 22.

The agency says its systems have not been targeted in a cyberattack and that the suspension is a precautionary measure.

Taxpayers can still prepare and file their returns online through another website that belongs to  the Agency.

The agency said it planned to restore access as soon as it can confirm that the system is secure.

The Japan Meteorological Agency also underwent emergency maintenance on its website on October 22, following the discovery of a critical vulnerability in the PHP programming language.

While disaster prevention information, including warnings and advisories, remains available, the agency’s latest and historical weather data are currently inaccessible. There is no estimated time for the maintenance to be completed.

The agency said it has not been targeted in a cyberattack and that the maintenance is being carried out as a precaution.

Other major companies in Japan have also suspended some online services in response to the security threat.

Mitsubishi UFJ Bank suspended online account openings and other services on October 21, citing temporary system maintenance.

Daiwa Securities has also suspended some online procedures, including account openings and address changes.

Part of Japan Airlines’ website has also been unavailable for maintenance. The airline said the disruption has not affected flight bookings or operations.

The companies have yet to announce when the affected services will resume.

The PHP vulnerability could allow attackers to manipulate systems remotely without authorization. PHP is used by approximately 70 percent of websites worldwide.

On October 21, the PHP development team released security patches and urged users to update their systems as soon as possible.

In Japan, Prime Minister Sanae Takaichi posted an urgent warning on X, urging organizations to check whether their public-facing websites use PHP and install the security patches promptly.

She also called on organizations to consider temporarily shutting down their websites if they cannot apply the fixes in a timely manner.

The websites of Prime Minister Takaichi and the Constitutional Democratic Party of Japan have also been taken offline as a precaution in response to the PHP security issue.

In addition, some content on the websites of the Ministry of Health, Labour and Welfare and the Ministry of Finance has reportedly been taken offline as a precautionary measure.

Outside Japan, several countries, including the Netherlands and Finland, have also temporarily suspended government-related websites as a precaution against potential cyberattacks.

The impact of the PHP vulnerability is continuing to spread, with more organizations suspending online services as a precaution. The full extent of the disruption remains unclear.