https://www.techpowerup.com/310478/asus-issues-router-product-security-advisory If you own one of several recent ASUS router models, then you're being urged by ASUS to upgrade your firmware to the latest release as soon as possible, due to a few serious security flaws. The two most severe being CVE-2022-26376 and CVE-2018-1160, both of which are rated 9.8 on a scale of 10 in terms of severity. However, if you're running the third party Asuswrt-Merlin firmware, you're apparently safe, as the author of the third party firmware has already patched all the known security issues that ASUS has announced patches for.
The affected models are the GT6, GT-AXE16000, GT-AX11000 PRO, GT-AX6000, GT-AX11000, GS-AX5400, GS-AX3000, XT9, XT8, XT8 V2, RT-AX86U PRO, RT-AX86U, RT-AX86S, RT-AX82U, RT-AX58U, RT-AX3000, TUF-AX6000, and TUF-AX5400. That's 18 different models in total, all of which should be built around Broadcom hardware. It's unclear if more models are affected or not, but these are the ones ASUS has issued updates for. The security flaws in question could allow someone to take over an unpatched router and make it a part of a botnet or similar. ASUS has suggested turning off features like DDNS and VPN servers, as well as more obvious things like WAN access, port forwarding, port triggers and DMZ until the firmware has been updated on the affected models.
Very important that if you have any of the models listed update your firmware at once.