The Easy Invoice plugin for WordPress is vulnerable to Missing Authorization in versions up to, and including, 2.1.19. This is due to the plugin registering the easyinvoiceacceptquote and easyinvoicedeclinequote AJAX actions via wpajaxnopriv hooks and relying solely on a quote-scoped nonce that is rendered into the publicly accessible single quote template, combined with an ownership check that is gated behind an off-by-default Pro option (easyinvoiceprorestrictquotetoclient). This makes it possible for unauthenticated attackers to accept or decline arbitrary published quotes — and, depending on the configured accept action, automatically convert them into invoices (and even email them to the client) — by harvesting the per-quote nonce from the public quote page and submitting it to admin-ajax.

Unauthenticated Remote Code Execution (RCE) in Easy Invoice <= 2.1.19 versions.