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+Update documentation for config setting `macaroon_secret_key`.
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diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
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 ---
 ### `macaroon_secret_key`
 
-A secret which is used to sign access tokens. If none is specified,
-the `registration_shared_secret` is used, if one is given; otherwise,
-a secret key is derived from the signing key.
+A secret which is used to sign
+- access token for guest users,
+- short-term login token used during SSO logins (OIDC or SAML2) and
+- token used for unsubscribing from email notifications.
+
+If none is specified, the `registration_shared_secret` is used, if one is given;
+otherwise, a secret key is derived from the signing key.
 
 Example configuration:
 ```yaml