Related Posts for WordPress <= 3.0.0 - Missing Authorization to Authenticated (Contributor+) Sensitive Information Exposure via 'rp4wp_create_link' Parameter

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.

Because it turns on account access, WordSec's login security is the relevant layer: role-based two-factor, captcha and brute-force limits raise the cost of getting the account this needs. None of that substitutes for the fix: Related Posts for WordPress 3.0.1 closes this, and updating the plugin is the step that ends it.

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