The Cryptocurrency Prijsvergelijking Widget plugin for WordPress is vulnerable to Stored Cross-Site Scripting in version 1.0. This is due to insufficient output escaping in the as_get_coin_shortcode() function, which renders the 'width' (and 'height') shortcode attribute directly into the style attribute of an <iframe> element without applying any escaping function such as esc_attr(). An attacker-controlled value like '100px;"onload="alert(1)" x="' terminates the style attribute prematurely and injects an arbitrary HTML attribute into the iframe tag. 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.