wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php:840Checks if the plugin is installed.
$pluginstringbool protected function is_plugin_installed( $plugin ) { return file_exists( WP_PLUGIN_DIR . '/' . $plugin ); }Introduced in 5.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.