Cross-site scripting in tstachl WordPress PayPal Donation

Summary

The WordPress PayPal Donation plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'donate' shortcode in all versions up to, and including, 1.01. This is due to insufficient input sanitization and output escaping on user-supplied shortcode attributes such as 'amount', 'email', 'title', 'return_url', 'cancel_url', 'ccode', and 'image'. The wordpress_paypal_donation_create() function uses extract(shortcode_atts(...)) to process shortcode attributes and then directly interpolates these values into HTML output within single-quoted attribute values without any escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.