An authentication bypass vulnerability exists in the WordPress Pie Register plugin ≤ 3.7.1.4 that allows unauthenticated attackers to impersonate arbitrary users by submitting a crafted POST request to the login endpoint. By setting social_site=true and manipulating the user_id_social_site parameter, an attacker can generate a valid WordPress session cookie for any user ID, including administrators. Once authenticated, the attacker may exploit plugin upload functionality to install a malicious plugin containing arbitrary PHP code, resulting in remote code execution on the underlying server.

AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CWE-94

CWE-306

CWE-434

https://github.com/GTSolutions/Pie-Register

https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/webapp/wp_pie_register_bypass_rce.rb

https://pieregister.com/

https://vulncheck.com/advisories/wordpress-pie-register-plugin-rce

https://wordpress.org/plugins/pie-register/

https://www.exploit-db.com/exploits/50395