Is Related Posts for WordPress safe? Known vulnerabilities and latest version

The Related Posts for WordPress plugin for WordPress is vulnerable to Sensitive Information Exposure in versions up to, and including, 3.0.0 via the 'rp4wp_create_link' parameter of the hidden 'rp4wp_link_related' admin page. The handle_create_link() handler verifies the nonce and that the current user can edit the parent post, but never checks that the attacker-supplied child post ID is one the user is allowed to read; LinkRepository::insert() stores the arbitrary child ID without validation, and ManageLinks::render() later calls LinkRepository::get_children() in its no-extra-args fast path, which falls through to array_map('get_post', $child_ids) — bypassing read_private_posts/read_post capability checks — and then echoes esc_html($child->post_title) in the parent's editor meta box. This makes it possible for authenticated attackers, with Contributor-level access and above, to read the titles of arbitrary non-public posts (drafts, pending, private, future, trashed) authored by higher-privileged users by linking those post IDs to a draft they own and then reading the resulting meta box.

The Related Posts for WordPress plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 3.0.0 via the 'rp4wp_view' parameter. This makes it possible for authenticated attackers, with contributor-level access and above, to extract the titles and publication dates of all private posts site-wide, normally restricted to Editor-level users and above. The page's existing authorization check only verifies edit_posts and edit_post on a parent post the attacker owns, both of which any Contributor satisfies, leaving no effective gate against reading other authors' private posts.

The Related Posts for WordPress plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 2.2.1. This is due to missing or incorrect nonce validation on the handle_create_link() function. This makes it possible for unauthenticated attackers to add related posts to other posts via a forged request granted they can trick a site administrator into performing an action such as clicking on a link. This ultimately makes it possible for attackers to view draft and password protected posts.

The Related Posts for WordPress plugin through 2.0.4 does not sanitise its heading_text and CSS settings, allowing high privilege users (admin) to set XSS payloads in them, leading to Stored Cross-Site Scripting issues.

Unvalidated input and lack of output encoding within the Related Posts for WordPress plugin before 2.0.4 lead to a Reflected Cross-Site Scripting (XSS) vulnerability within the 'lang' GET parameter while editing a post, triggered when users with the capability of editing posts access a malicious URL.