The VikRentCar Car Rental Management System plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'className' parameter in all versions up to, and including, 1.4.10 due to insufficient input sanitization and output 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. wp_kses_post() applied at save time does not neutralize the payload because the injection lands in an HTML-attribute context where only a raw double-quote is needed to break out, and block-comment JSON encoding of that quote is decoded back to a literal character by do_blocks() at render time.