1) Add a new callback to  /mod/assign/lib.php function mod_assign_security_checks() { return [ new mod_assign\check\foobar()]; } And make a new check class in mod/assign/classes/check/foobar.php <?php namespace mod_assign\check; use core\check\check;   class foobar extends check { public function __construct() { $this ->id = 'foobar' ; $this ->name = 'my foobar check' ; $this ->status = check::ERROR; $this ->summary = 'foobar summary' ; $this ->details = 'some <b>details!</b>' ; } } 2) Purge cache php admin/cli/purge_caches.php 3) Visit /report/security/index.php Confirm you can see a new 'foobar' check which is failing 4) Click on the Foo bar link and confirm you can see the details