Critical remote code execution vulnerabilities were
announced yesterday by the PHP team, and all miniBB admins should take the closest attention to this issue.
There is no deal with miniBB itself, as also it doesn't depend on any PHP program you have.
The only-workaround is to update your PHP version either to PHP
8.5.12, 8.4.27, 8.3.36 or 8.2.35, which fix these vulnerabilities. Older PHP versions do not contain the fixes:
php.net:
PHP 8.1 and older no longer receive updates from the PHP project.
On your server, you should at least have PHP 8.2.35, but keep in mind that
PHP 8.2 reaches end of life on 31 December 2026 and will receive no further security fixes after that date.
So — switching to at least PHP 8.3.36 would be the reasonable move now.
Request this from your hoster!