CVE-2021-24147

Modern Events Calendar Lite <= 5.16.4 - Authenticated Stored Cross-Site Scripting

2021-01-29 00:00
Nguyen Van Khanh

Strategic Overview

Status
Patched in 5.16.5
Affected Plugin
Modern Events Calendar Lite
Affected Version
<= 5.16.4
CVSS
6.4Medium
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2021-24147
View all Modern Events Calendar Lite vulnerabilities

At a glance

CVE-2021-24147 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Modern Events Calendar Lite WordPress plugin, affecting versions <= 5.16.4. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). Exploitation requires an authenticated account. The issue is fixed in version 5.16.5; sites on affected versions should update now. Disclosed January 2021, reported by Nguyen Van Khanh.

Vulnerability Overview

Unvalidated input and lack of output encoding in the Modern Events Calendar Lite WordPress plugin, versions before 5.16.5, did not sanitise the mic_comment field (Notes on time) when adding/editing an event, allowing users with privilege as low as author to add events with a Cross-Site Scripting payload in them, which will be triggered in the frontend when viewing the event.

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 Modern Events Calendar Lite <= 5.16.4 takes any authenticated account. 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 Modern Events Calendar Lite the fix is 5.16.5: builds <= 5.16.4 are affected, anything from 5.16.5 onward is not.

Remediation

Update to version 5.16.5, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Modern Events Calendar Lite: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Modern Events Calendar Lite 5.16.5 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2021-24147https://www.wordfence.com/threat-intel/vulnerabilities/id/b3aa7b27-a335-4f82-a50a-45becdd5ef4ehttps://nvd.nist.gov/vuln/detail/CVE-2021-24147

Related records

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