https://www.zyxel.com/us/en/support/vulnerabilities-related-to-the-Free-Time-feature.shtml

http://secure.campaigner.com/csb/Public/show/d9wg-2evy1r–v7ugq-ds0etcv9

https://eye.security/en/blog/undocumented-user-account-in-zyxel-products-cve-2020-29583