Arbitrary shortcode execution in ProfilePress user profile comments

The WP User Avatar / ProfilePress plugin for WordPress is vulnerable to Arbitrary Shortcode Execution in versions up to, and including, 4.17.5. This is due to the get_user_profile_structure() function assembling the front-end profile buffer — which includes raw comment excerpts inlined by author_comment_query() — and passing the entire buffer to do_shortcode() after only a narrow neutralization pass (ppress_neutralize_buffer_shortcodes) that blocks pp-custom-html and bracket fragments containing HTML delimiters but leaves any other well-formed shortcode intact. This makes it possible for authenticated attackers, with Subscriber-level access and above, to inject arbitrary shortcodes (from any active plugin or theme) with attacker-chosen attributes by posting a comment whose body contains the shortcode markup; the shortcode is then executed server-side when any visitor loads the target's front-end profile Comments tab, letting the attacker reach capability-gated or data-returning shortcodes and inject raw HTML markup into a publicly viewable page.