CVE-2020-36847

Simple File List, a WordPress plugin for publishing downloadable file lists, is vulnerable to unauthenticated remote code execution in all versions up to and including 4.2.2 (CWE-434). The flaw is in the plugin's rename function: an attacker first uploads a file containing PHP code with a harmless .png extension, then abuses the rename function to change that file's extension to .php, turning the upload into an executable script on the server. Because the upload and rename operations require no authentication, any remote attacker can run arbitrary code on the web server, which can lead to complete site compromise, webshells, or backdoor installation. All WordPress sites running Simple File List 4.2.2 or earlier are affected, on the order of tens of thousands of installations based on the plugin's active-install count. Public proof-of-concept exploits are available and the vulnerability carries a high EPSS score (44.7% probability of exploitation in 30 days, 99th percentile), though it is not yet listed in CISA's Known Exploited Vulnerabilities catalog.

What to do: Update Simple File List to the latest release (any version newer than 4.2.2); there is no configuration mitigation since the attack requires no authentication. Until patched, check the plugin's upload directory for unexpected .php files and renamed .png uploads, and review web server logs for unauthenticated requests to the plugin's upload/rename endpoints. Given ongoing WordPress plugin exploitation campaigns reported in 2026 (e.g., WP-SHELLSTORM), also scan already-patched sites for webshells and backdoors in case exploitation already occurred.