The application relates to a multi-link device and a method performed therein. An access point multi-link device (AP MLD) includes a plurality of APs, each of which comprises: a wireless medium; and processor circuitry coupled to the wireless medium and configured to: transmit security capability indication information via the wireless medium; receive an association request frame from a non-AP MLD via the wireless medium, wherein the association request frame comprises security capability indication information of the plurality of non-AP STAs; determine whether the security capability indication information of any of the plurality of non-AP STAs matches with the security capability indication information of the AP; and if the security capability indication information of one of the plurality of non-AP STAs matches with the security capability information of the AP, transmit an association response frame to the non-AP MLD via the wireless medium.