To ensure your guest community users can securely log cases directly through contact support, enable Guest Access to the Support API and add NewCase to the quick actions.
- From Setup, enter Communities in the Quick Find box, then select All Communities.
- Select Manage next to the community you want your guest users to log cases via contact support.
- On the left-hand panel, click Administration.
- Click Pages.
- Click Go to Force.com.
- On the Sites Detail page, click Edit.
- Enable Guest Access to the Support API.
- Add NewCase, or a custom quick action to add cases, to the Selected Quick Actions.
- Click Save.