The Simple Newsletter Plugin – Noptin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'noptinfields[<customfieldmergetag>] (e.g. firstname)' parameter in all versions up to, and including, 4.3.10 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The attack chain requires a published campaign post whose body contains a [[subscriber.]] merge tag; the unauthenticated attacker first POSTs the entity-encoded payload to the public managepreferences form (which issues its own nonce on the same page), then pivots execution by embedding their confirmkey in a campaign preview URL sent to a privileged user via social engineering.

Missing Authorization vulnerability in Noptin Newsletter Noptin allows Accessing Functionality Not Properly Constrained by ACLs.This issue affects Noptin: from n/a through 3.4.2.

A vulnerability in Noptin Newsletter Team Noptin newsletter-optin-box.This issue affects Noptin: from n/a through <= 1.9.5.

The WordPress Newsletter Plugin WordPress plugin before 1.6.5 does not validate the to parameter before redirecting the user to its given value, leading to an open redirect issue