MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. <= 1.2.78.0 - Authenticated (Contributor+) Stored Cross-Site Scripting
Strategic Overview
- Status
- Patched in 1.2.78.1
- Affected Plugin
- MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.
- Affected Version
<= 1.2.78.0- CVSS
- 6.4Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2026-66703
At a glance
CVE-2026-66703 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the MailOptin WordPress plugin, affecting versions <= 1.2.78.0. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). Exploitation requires an authenticated account at Contributor level or above. The issue is fixed in version 1.2.78.1; sites on affected versions should update now. Disclosed July 2026, reported by Ananda Dhakal.
Vulnerability Overview
The MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 1.2.78.0 due to insufficient input sanitization and output escaping. 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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Reaching this weakness in MailOptin <= 1.2.78.0 takes an account at Contributor level or above. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.
Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For MailOptin the fix is 1.2.78.1: builds <= 1.2.78.0 are affected, anything from 1.2.78.1 onward is not.
Remediation
Update to version 1.2.78.1, or a newer patched version
How WordSec helps
An attacker needs Contributor access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: MailOptin 1.2.78.1 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Same weakness class
Other vulnerabilities in MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.
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