CVE-2026-78159

The Events Calendar <= 6.17.3 - Unauthenticated Code Injection to Remote Code Execution via Widget 'classes' Map Callable Invocation

2026-09-11 18:40
Chloe Chamberland

Strategic Overview

Status
Patched in 6.17.3.1
Affected Plugin
The Events Calendar
Affected Version
<= 6.17.3
CVSS
9.8Critical
Weakness type
CWE-94 · Improper Control of Generation of Code ('Code Injection')
CVE
CVE-2026-78159
View all The Events Calendar vulnerabilities

At a glance

CVE-2026-78159 is a critical-severity Improper Control of Generation of Code ('Code Injection') vulnerability in the The Events Calendar WordPress plugin, affecting versions <= 6.17.3. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 6.17.3.1; sites on affected versions should update now. Disclosed September 2026, reported by Chloe Chamberland.

Vulnerability Overview

The The Events Calendar plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 6.17.3 via the parse_array function. This is due to insufficient validation of the widget 'classes' map, allowing a plain-array payload to bypass the is_safe_widget_instance() object check and reach the callable-invocation sink in Element_Classes::parse_array(). This makes it possible for unauthenticated attackers to execute code on the server. Exploitation requires that the targeted site has comments enabled on tribe_events posts and that at least one comment containing a crafted wp:legacy-widget block has been submitted, as the attack chain is triggered when do_blocks() processes the single-event HTML including the comment area.

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 privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.

CWE-94: Improper Control of Generation of Code ('Code Injection')

The Events Calendar <= 6.17.3 carries this weakness at classes, and reaching it takes no account at all. Code injection means input from a request reaches a language construct that evaluates code, so the attacker's text is executed rather than treated as data.

The injected code runs with the web server's privileges, giving the attacker the same access to the database and filesystem as WordPress itself. For The Events Calendar the fix is 6.17.3.1: builds <= 6.17.3 are affected, anything from 6.17.3.1 onward is not.

Remediation

Update to version 6.17.3.1, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: The Events Calendar 6.17.3.1 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Scanner
  • Login Security

External References

https://www.cve.org/CVERecord?id=CVE-2026-78159https://www.wordfence.com/threat-intel/vulnerabilities/id/cc2ccfeb-6df6-4fee-96a5-94f8dd131f7chttps://nvd.nist.gov/vuln/detail/CVE-2026-78159

Related records

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