CVE-2026-92537: Newsletter <= 9.3.9 - Unauthenticated Insufficiently Protected Credentials via '/tnp/l/' Click-Tracking REST Endpoint (Raw Subscriber Token Cookie Disclosure)
The Newsletter – Send awesome emails from WordPress plugin for WordPress is vulnerable to Insufficiently Protected Credentials in all versions up to, and including, 9.3.9 The plugin's public click-tracking REST route /tnp/l/ is registered with permissioncallback => 'returntrue' and, upon receiving a valid keyed-MD5 signature, calls setusercookie(), which emits a Set-Cookie: newsletter=<id>-<rawtoken> response header to the requester because the subscriber object loaded via getuser() lacks the trusted property, causing getuserkey() to return the raw token column value instead of its MD5-masked variant. This makes it possible for unauthenticated attackers who obtain any signed click-tracking URL for a target subscriber to receive that subscriber's permanent raw authentication cookie, which they can then use to export the subscriber's full PII record via the JSON profile-export endpoint (?na=px), rewrite the subscriber's stored profile (?na=ps), and silently unsubscribe the subscriber via the RFC-8058 one-click endpoint (?na=ocu), none of which require a nonce, password, or email challenge. Signed tracking URLs are embedded in every external link of every newsletter delivered to a subscriber, carry no timestamp, and never expire until the site's relink key rotates, meaning that any party who observes such a URL — through a forwarded email, a shared inbox, a mail-gateway log, or Referer headers on the redirect target, which has no Referrer-Policy set — can replay it indefinitely to obtain the victim's credential.
Affected Software
Event History
Frequently Asked Questions
Who is exposed to this issue?
Sites using the affected plugin versions up to and including 9.3.9 are exposed. Any subscriber whose signed click-tracking URL is obtained by an attacker may be affected.
What does an attacker need to exploit it?
The attacker needs a valid keyed-MD5-signed click-tracking URL for the target subscriber. No WordPress authentication, nonce, password, email challenge, or user interaction is required.
Are default tracking links relevant?
Yes. Signed tracking URLs are embedded in external links, so exposure depends on an attacker obtaining one of those URLs for a subscriber.
What can an attacker do with the disclosed cookie?
The cookie can be used to export the subscriber's full PII record, modify the subscriber's stored profile, or silently unsubscribe the subscriber through the one-click unsubscribe endpoint.
How can I determine whether a subscriber may have been affected?
Review whether signed click-tracking URLs for subscribers may have been exposed to untrusted parties. The provided information does not identify a specific log entry or other definitive indicator of exploitation.