CVE-2026-111727: XSS (CVSS 6.4)

Description

The Appointment Booking Calendar plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'vs_text_submitbtn' parameter in all versions up to, and including, 1.4.05 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the attacker to be assigned as a calendar owner, a per-user grant that any administrator can extend to users as low as Subscriber level through the plugin's calendar list screen. Exploitation by attackers with subscriber-level access and above requires that an administrator has assigned the attacker's account as owner (`conwer`) of a calendar via the plugin's calendar list screen; the plugin's UI lists all registered users regardless of role, so a Subscriber can be assigned. On a default installation, where that is not configured, the vulnerability requires attackers with editor-level access and above.

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CVSS v3.1 Score

6.4

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0021

Probability of exploitation

0.11%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

References

Other References

https://plugins.trac.wordpress.org/browser/appointment-booking-calendar/tags/1.4.05/inc/cpabc_apps_go.inc.php#L102 https://plugins.trac.wordpress.org/browser/appointment-booking-calendar/tags/1.4.05/inc/cpabc_apps_go.inc.php#L616 https://plugins.trac.wordpress.org/browser/appointment-booking-calendar/tags/1.4.05/inc/cpabc_apps_go.inc.php#L690 https://plugins.trac.wordpress.org/browser/appointment-booking-calendar/tags/1.4.05/inc/cpabc_apps_on.inc.php#L398 https://plugins.trac.wordpress.org/browser/appointment-booking-calendar/tags/1.4.05/inc/cpabc_scheduler.inc.php#L194 https://plugins.trac.wordpress.org/changeset/3750835/appointment-booking-calendar/trunk/inc/cpabc_scheduler.inc.php https://plugins.trac.wordpress.org/log/appointment-booking-calendar/ https://www.wordfence.com/threat-intel/vulnerabilities/id/dd0e4753-222a-421f-a830-58f6af055dd8?source=cve

Frequently Asked Questions

What is CVE-2026-111727? +

The Appointment Booking Calendar plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'vs_text_submitbtn' parameter in all versions up to, and including, 1.4.05 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the attacker to be assigned as a calendar owner, a per-user grant that any administrator can extend to users as low as Subscriber level through the plugin's calendar list screen. Exploitation by attackers with subscriber-level access and above requires that an administrator has assigned the attacker's account as owner (`conwer`) of a calendar via the plugin's calendar list screen; the plugin's UI lists all registered users regardless of role, so a Subscriber can be assigned. On a default installation, where that is not configured, the vulnerability requires attackers with editor-level access and above. It has a CVSS v3.1 base score of 6.4 (MEDIUM).

How severe is CVE-2026-111727? +

CVE-2026-111727 has a CVSS v3.1 score of 6.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0021, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-111727? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-111727