Before you even think about downloading a file, remember this rule: Do not upgrade across major versions blindly. If your panel is running firmware V1.x, jumping straight to V2.x or V3.x often requires an intermediate "bridge" firmware. Skipping this step can "brick" the device, leaving it unresponsive.
Do not trust random file locker sites.
HikCentral allows administrators to push firmware to multiple controllers simultaneously. Schedule updates during off-hours (e.g., 2 AM Sunday). The dashboard will show which devices succeeded or failed. ds-k2604t firmware