Newsletter – Send awesome emails from WordPress: Tracking URLs expose permanent subscriber credentials

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 `permission_callback => '__return_true'` and, upon receiving a valid keyed-MD5 signature, calls `set_user_cookie()`, which emits a `Set-Cookie: newsletter=-` response header to the requester because the subscriber object loaded via `get_user()` lacks the `_trusted` property, causing `get_user_key()` 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. The official changelog confirms a matching fix in 9.4.0.

CVE / CNA score 5.3 CVSS 3.1 · security@wordfence.com

NVD score Pending NVD has not published its own CVSS assessment.

Component: Newsletter – Send awesome emails from WordPress
Plugin slug: newsletter
Affected: <= 9.3.9
Safe version: 9.4.0
Published: Oct 01, 2026
Weakness: CWE-522 — Insufficiently Protected Credentials

This CVE was published Oct 01, 2026 and is one of 21 known issues for this plugin.

What to do

Update, patch or deactivate.

Update Newsletter – Send awesome emails from WordPress to 9.4.0 or a later supported release. Do not exchange a tracking URL for a permanent raw subscriber credential. Separate tracking from profile authorization and invalidate exposed subscriber tokens after upgrading.

A safe version is available, so updating to that version or later is the preferred remediation. If an immediate update is not practical, consider a targeted application patch or temporarily restricting the affected functionality.

Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.

Source record

Technical description

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 `permission_callback => '__return_true'` and, upon receiving a valid keyed-MD5 signature, calls `set_user_cookie()`, which emits a `Set-Cookie: newsletter=<id>-<raw_token>` response header to the requester because the subscriber object loaded via `get_user()` lacks the `_trusted` property, causing `get_user_key()` 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.

CVE / CNA vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References

Primary and upstream sources

Data attribution: This product uses the NVD API but is not endorsed or certified by the NVD.

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