CVE-2018-20756: Modx/revolution Remote Code Execution Vulnerability

MODERATE
Advisory Identifier: GHSA-fpxg-5x79-43rm
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CVSS 6.1
CWE-79
Published
Advisory Summary

CVE-2018-20756 is a MODERATE (CVSS 6.1) remote code execution vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Modx/revolution libraries in the Packagist ecosystem. The issue involves modx revolution allows xss via document resources. Remediation is available by upgrading affected packages to version 2.7.1-pl.

CVE-2018-20756 at a Glance

CVE Identifier CVE-2018-20756
GHSA Identifier GHSA-fpxg-5x79-43rm
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Modx/revolution
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2018-20756

To remediate this vulnerability, upgrade all affected Modx/revolution dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

modx/revolution fixed: 2.7.1-pl 
Upgrade modx/revolution to 2.7.1-pl
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for modx/revolution

How to Check if You Are Affected

To determine whether your application is affected by CVE-2018-20756, inspect your project dependencies for Modx/revolution:

inspect dependencies for modx/revolution

Analyze the terminal output to locate any version of Modx/revolution in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.7.1-pl), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Modx/revolution, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

MODX Revolution through v2.7.0-pl allows XSS via a document resource (such as pagetitle), which is mishandled during an Update action, a Quick Edit action, or the viewing of manager logs.

CVE-2018-20756 Affected Modx/revolution Versions

1 component(s)
Fixed Versions:
2.7.1-pl
Product / Package Ecosystem Affected Versions Fixed Version
modx/revolution
 Packagist
< 2.7.1-pl
2.7.1-pl

References

NVD — CVE-2018-20756 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20756
Modx/revolution Source Repository REPOSITORY
https://github.com/modxcms/revolution/issues/14105
Modx/revolution Source Repository REPOSITORY
https://github.com/modxcms/revolution/pull/14335
Security Fix Commit FIX COMMIT
https://github.com/modxcms/revolution/commit/71f894ee55dc4eed10538979761d6c94e8cd1078
Modx/revolution Source Repository REPOSITORY
https://github.com/modxcms/revolution

Frequently Asked Questions

What is CVE-2018-20756?
CVE-2018-20756 is a security vulnerability in Modx/revolution involving MODX Revolution allows XSS via document resources under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Modx/revolution versions are affected?
Affected versions include releases prior to 2.7.1-pl across affected packages: modx/revolution.
What version fixes CVE-2018-20756?
Upgrading to 2.7.1-pl (or the latest patched release for your respective branch) resolves the vulnerability.
Is modx/revolution affected?
Yes, modx/revolution is affected in releases prior to 2.7.1-pl. Upgrade your dependency to 2.7.1-pl or later.
What is the CVSS score of CVE-2018-20756?
CVE-2018-20756 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2018-20756?
CVE-2018-20756 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Packagist dependencies for CVE-2018-20756?
Run the dependency tree command: 'inspect dependencies for modx/revolution'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fpxg-5x79-43rm",
  "modified" : "2025-07-11T22:47:26Z",
  "published" : "2022-05-14T01:36:14Z",
  "aliases" : [ "CVE-2018-20756" ],
  "summary" : "MODX Revolution allows XSS via document resources",
  "details" : "MODX Revolution through v2.7.0-pl allows XSS via a document resource (such as pagetitle), which is mishandled during an Update action, a Quick Edit action, or the viewing of manager logs.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "modx/revolution"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.7.1-pl"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20756"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/modxcms/revolution/issues/14105"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/modxcms/revolution/pull/14335"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/modxcms/revolution/commit/71f894ee55dc4eed10538979761d6c94e8cd1078"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/modxcms/revolution"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-07-11T22:47:26Z",
    "nvd_published_at" : "2019-02-06T17:29:00Z"
  }
}