An issue was discovered on Dasan GPON home routers. It is possible to bypass authentication simply by appending "?images" to any URL of the device that requires authentication, as demonstrated by the /menu.html?images/ or /GponForm/diag_FORM?images/ URI. One can then manage the device.
https://blog.xlab.qianxin.com/catddos-derivative-en/
https://www.avira.com/en/blog/a-gafgyt-variant-that-exploits-pulse-secure-cve-2020-8218
https://www.vpnmentor.com/blog/critical-vulnerability-gpon-router/