Improper Validation of Specified Quantity in Input vulnerability in Tips and Tricks HQ WP Express Checkout (Accept PayPal Payments) allows Manipulating Hidden Fields.This issue affects WP Express Checkout (Accept PayPal Payments): from n/a through 2.3.7.

The WP Express Checkout plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘pec_coupon[code]’ parameter in versions up to, and including, 2.2.8 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers with administrator-level access to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. Note: This can potentially be exploited by lower-privileged users if the `Admin Dashboard Access Permission` setting it set for those users to access the dashboard.