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.
CVE-2026-3475
Score 5.3 from GitHub Security Advisory published 2026-03-19. NVD baseline CVSS 5.3; sources differ by 0.0.
- Lower severity and no public exploit yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 5.3
- EG Score
- 5.3(medium)
- EPSS
- 19.9%
- KEV
- Not listed
Published
March 19, 2026
Last Modified
April 22, 2026
References (6)
- security@wordfencehttps://plugins.trac.wordpress.org/browser/instant-popup-builder/tags/1.1.6/public/class-instant-popup-subscription-public.php#L1761
- security@wordfencehttps://plugins.trac.wordpress.org/browser/instant-popup-builder/tags/1.1.6/public/class-instant-popup-subscription-public.php#L1772
- security@wordfencehttps://plugins.trac.wordpress.org/browser/instant-popup-builder/trunk/public/class-instant-popup-subscription-public.php#L1761
- security@wordfencehttps://plugins.trac.wordpress.org/browser/instant-popup-builder/trunk/public/class-instant-popup-subscription-public.php#L1772
- security@wordfencehttps://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&old=3477334%40instant-popup-builder&new=3477334%40instant-popup-builder&sfp_email=&sfph_mail=
- security@wordfencehttps://www.wordfence.com/threat-intel/vulnerabilities/id/979962e3-9052-4dc9-94d0-3ec8de3d5460?source=cve
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 8× in last 7d / 35× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
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Related CVEs(same CWE)
Same CWE
10 shownCWE-862
Frequently asked(5)
What is CVE-2026-3475?
When was CVE-2026-3475 disclosed?
Is CVE-2026-3475 actively exploited?
What is the CVSS score of CVE-2026-3475?
How do I remediate CVE-2026-3475?
Dependency Blast Radius
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