CVE-2026-86583: Import and export users and customers <= 2.4.17 - Authenticated (Subscriber+) Privilege Escalation via CSV Escape-Character Mismatch in Export/Import Round Trip via display_name and nickname Profile Fields

The Import and export users and customers plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 2.4.17 via the plugin's own export and re-import workflow. The vulnerability exists because the exporter writes CSV cells using fputcsv() with a NUL byte (\0) as the escape character, while the importer parses the same file using SplFileObject::fgetcsv() with only a single delimiter argument, causing PHP's default backslash escape character to be applied instead; because the export column layout places displayname immediately before the role column and nickname immediately after, an attacker can store crafted values in those two profile fields — saved by WordPress core via the standard profile page — such that the escape mismatch causes the parser to merge the displayname cell into the role field and rebalance the column count via nickname, yielding administrator as the parsed role for their own row when it reaches the importuser function's addrole function. This makes it possible for authenticated attackers with Subscriber-level access or above to escalate their privileges to Administrator. Exploitation requires a site administrator to trigger the plugin's documented export re-import migration with both "Update existing users" and "Update roles for existing users" set to "yes".