Draft List <= 2.6.2 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'display_name' Parameter

The Simple Draft List plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'display_name' post meta (Custom Field) in all versions up to and including 2.6.2. This is due to insufficient input sanitization and output escaping on the author display name when no author URL is present. The plugin accesses `$draft_data->display_name` which, because `display_name` is not a native WP_Post property, triggers WP_Post::__get() and resolves to `get_post_meta($post_id, 'display_name', true)`. When the `user_url` meta field is empty, the `$author` value is assigned to `$author_link` on line 383 without any escaping (unlike line 378 which uses `esc_html()` for the `{{author}}` tag, and line 381 which uses `esc_html()` when a URL is present). This unescaped value is then inserted into the shortcode output via `str_replace()`. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses a page containing the `[drafts]` shortcode with the `{{author+link}}` template tag.