Stop Spammers Classic <= 2026.6 - Unauthenticated Stored Cross-Site Scripting via 'author' Parameter

The Stop Spammers Classic plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'author' POST parameter in versions up to, and including, 2026.6. An unauthenticated POST handled on init stores the attacker-supplied author field (after sanitize_text_field, which does not escape single quotes) into the ss_stop_sp_reg_stats option history. The Log Report admin page then renders that stored value inside a single-quoted JavaScript string within a double-quoted onclick attribute using esc_js(); because esc_js() uses _wp_specialchars with ENT_COMPAT it does not escape single quotes, allowing the stored value to break out of the JS string literal and inject arbitrary JavaScript. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute whenever an administrator with manage_options access clicks the 'Report to SFS' link on an attacker-poisoned log row (the StopForumSpam API key must be configured for that link to be rendered — the field is empty by default). Successful exploitation additionally requires an action by an administrator — the attacker cannot trigger the vulnerability on their own.

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Stop Spammers Classic 2026.7 closes this, and updating the plugin is the step that ends it.

• Firewall
• Login Security
• Alerts