CVE-2026-3475 Instant Popup Builder <= 1.1.7 - Unauthenticated Arbitrary Shortcode Execution via 'token' Parameter
Unauthenticated attackers can execute arbitrary shortcodes via the token parameter in Instant Popup Builder, potentially leading to code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-3475?
CVE-2026-3475 is a medium-severity code injection vulnerability in instantpopupbuilder Instant Popup Builder – Powerful Popup Maker for Opt-ins, Email Newsletters & Lead Generation, published on 19 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The Instant Popup Builder plugin for WordPress is vulnerable to Unauthenticated Arbitrary Shortcode Execution in all versions up to and including 1.1.7. This is due to the handle_email_verification_page() function constructing a shortcode string from user-supplied GET parameters (token, email) and passing it to do_shortcode() without properly sanitizing square bracket characters, combined with missing authorization checks on the init hook. While sanitize_text_field() and esc_attr() are applied, neither function strips or escapes square bracket characters ([ and ]). WordPress's shortcode regex uses [^\]\/]* to match content inside shortcode tags, meaning a ] character in the token value prematurely closes the shortcode tag. This makes it possible for unauthenticated attackers to inject and execute arbitrary registered shortcodes by crafting a malicious token parameter containing ] followed by arbitrary shortcode syntax.
Weakness: CWE-862
Which versions are affected by CVE-2026-3475?
How do I fix CVE-2026-3475?
No fix has been published for CVE-2026-3475 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-3475 being exploited?
There is no known exploitation of CVE-2026-3475 in the wild and no public exploit code.
Sources
Also known as GHSA-9c7f-g6v7-xwq7.