CVE-2026-12939 Newsletters <= 4.15 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'link' Shortcode Attribute
Authenticated contributors can inject arbitrary scripts via the link shortcode attribute, leading to stored XSS execution for other users.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-12939?
CVE-2026-12939 is a medium-severity cross-site scripting vulnerability in contrid Newsletters, published on 29 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
The Newsletters Lite plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'link' attribute of the post_thumbnail (and newsletters_post_thumbnail) shortcodes in versions up to and including 4.15. This is due to insufficient input sanitization and output escaping in the post_thumbnail() method in helpers/shortcode.php, which concatenates the user-controlled $link shortcode attribute directly into an href attribute without esc_url() or esc_attr(). 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-12939?
How do I fix CVE-2026-12939?
No fix has been published for CVE-2026-12939 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-12939 being exploited?
There is no known exploitation of CVE-2026-12939 in the wild and no public exploit code.
Sources
Also known as GHSA-x3c9-qfw8-8r9c.