Is running an old ASUS Merlin Router as and AP a security risk?

[AsusRouterUser]

I have a old RT-AC56U that is no longer supported, if I want to run it in AP Mode behind another router is it a security risk on the wifi side because of no updates?

 

[Tech9]

Potential security risk, but exploitable only locally from whoever sees your Wi-Fi and has specific skill set needed. I would say safe to use as AP since the risk level is very low and issues are unlikely. Use stock Asuswrt on it, it's newer release than last Asuswrt-Merlin.

https://www.asus.com/supportonly/rt-ac56u/helpdesk_bios/