Easy native HTML5 forms for WordPress. Version 1.5 is unmaintained, but works without issue. 2.0 has been rewritten from the ground, and can be found at https://github.com/libreform/libreform
If permission_callback argument is not given, the following error will occur :
Notice: register_rest_route was called incorrectly. The REST API route definition for wplf/v1/submit is missing the required permission_callback argument. For REST API routes that are intended to be public, use __return_true as the permission callback. Please see Debugging in WordPress for more information. (This message was added in version 5.5.0.)
This is due to the recent change in WordPress Core: https://make.wordpress.org/core/2020/07/22/rest-api-changes-in-wordpress-5-5/
If permission_callback argument is not given, the following error will occur :
Notice: register_rest_route was called incorrectly. The REST API route definition for wplf/v1/submit is missing the required permission_callback argument. For REST API routes that are intended to be public, use __return_true as the permission callback. Please see Debugging in WordPress for more information. (This message was added in version 5.5.0.)