The “Web Hook Auth Keys” option is located in Memberium => Settings => Web Hooks/Links tab. This option allows you to define one or more authentication keys for Memberium web hooks.
For best security practices you should not reuse or tie your web hook auth keys to your ActiveCampaign API key, or to your autologin auth keys.
You can define multiple auth keys by separating each one with a comma. This makes it easy to transition from one key to another by having multiple active keys at once.