The manufacturers should release "firmware" updates; they update the software in the router and fix vulnerabilities or add features. Your D-Link router from 20

The manufacturers should release "firmware" updates; they update the software in the router and fix vulnerabilities or add features. Your D-Link router from 2014 likely stopped receiving updates within 2-4 years of its manufacture so updating now will still leave you quite outdated, if the manufacturer released any updates at all (and if they did, they may even have pulled them offline as we're now 10 years after the fact). If you're concerned about the security, you can check if your router is supported by an open-source OS like OpenWRT and flash that over the factory software, or upgrade to a newer model (bearing in mind another consumer router will only get you a few short more years of updates). If you're really cautious (like I am) you buy something that you can install a router OS on that you know will always be updated; pfSense, OPNSense, OpenWRT, Vy etc.