Lots of “Deprecated: Creation of dynamic property..”

Hello,
more and more hosting providers are upgrading PHP and now, if I enable debug mode, I get an endless stream of warnings, like:

Deprecated: Creation of dynamic property WP_Post_Author_Core::$id is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/core.php on line 28

Deprecated: Creation of dynamic property WP_Post_Author_Core::$method_title is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/core.php on line 29

Deprecated: Creation of dynamic property WP_Post_Author_Core::$method_description is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/core.php on line 30

Deprecated: Creation of dynamic property WP_Post_Author_Backend::$id is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-backend.php on line 27

Deprecated: Creation of dynamic property WP_Post_Author_Backend::$method_title is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-backend.php on line 28

Deprecated: Creation of dynamic property WP_Post_Author_Backend::$method_description is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-backend.php on line 29

Deprecated: Creation of dynamic property WP_Post_Author_User_Fields::$id is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-user-fields.php on line 27

Deprecated: Creation of dynamic property WP_Post_Author_User_Fields::$method_title is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-user-fields.php on line 28

Deprecated: Creation of dynamic property WP_Post_Author_User_Fields::$method_description is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-user-fields.php on line 29

Deprecated: Creation of dynamic property WP_Post_Author_Frontend::$id is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-frontend.php on line 28

Deprecated: Creation of dynamic property WP_Post_Author_Frontend::$method_title is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-frontend.php on line 29

Deprecated: Creation of dynamic property WP_Post_Author_Frontend::$method_description is deprecated in /var/www/.../wp-content/plugins/wp-post-author/includes/awpa-frontend.php on line 30

I suggest you either upgrade your code or implement the simple #[AllowDynamicProperties] attribute as suggested in this StackOverflow post.