CVE-2020-17480: Tinymce Cross-Site Scripting Vulnerability

HIGH
Advisory Identifier: GHSA-27gm-ghr9-4v95
Share
CWE-79
Published
Advisory Summary

CVE-2020-17480 is a HIGH cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Tinymce libraries in the npm ecosystem. The issue involves cross-site scripting vulnerability in tinymce. Remediation is available by upgrading affected packages to version 4.9.7, 5.1.4.

CVE-2020-17480 at a Glance

CVE Identifier CVE-2020-17480
GHSA Identifier GHSA-27gm-ghr9-4v95
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Tinymce
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2020-17480

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

tinymce fixed: 4.9.7 
npm install tinymce@4.9.7
tinymce fixed: 5.1.4 
npm install tinymce@5.1.4
Verify Direct and Transitive Dependencies

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

npm ls tinymce

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2020-17480, inspect your project dependencies using npm:

npm ls tinymce

Analyze the terminal output to locate any version of Tinymce in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.9.7), your application is affected.

Note: The npm ls tinymce command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

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 Tinymce, 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

### Impact A cross-site scripting (XSS) vulnerability was discovered in: the core parser, `paste` and `visualchars` plugins. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor via the clipboard or APIs. This impacts all users who are using TinyMCE 4.9.6 or lower and TinyMCE 5.1.3 or lower. ### Patches This vulnerability has been patched in TinyMCE 4.9.7 and 5.1.4 by improved parser logic and HTML sanitization. ### Workarounds The workarounds available are: - disable the impacted plugins - manually sanitize the content using the `BeforeSetContent` event (see below) - upgrade to either TinyMCE 4.9.7 or TinyMCE 5.1.4 #### Example: Manually sanitize content ```js editor.on('BeforeSetContent', function(e) { var sanitizedContent = ...; // Manually sanitize content here e.content = sanitizedContent; }); ``` ### Acknowledgements Tiny Technologies would like to thank Michał Bentkowski for discovering this vulnerability. ### References https://www.tiny.cloud/docs/release-notes/release-notes514/#securityfixes ### For more information If you have any questions or comments about this advisory: * Open an issue in the [TinyMCE repo](https://github.com/tinymce/tinymce/issues) * Email us at [infosec@tiny.cloud](mailto:infosec@tiny.cloud)

CVE-2020-17480 Affected Tinymce Versions

2 component(s)
Fixed Versions:
4.9.75.1.4
Product / Package Ecosystem Affected Versions Fixed Version
tinymce
npm/tinymce
npm
< 4.9.7
4.9.7
tinymce
npm/tinymce
npm
≥ 5.0.0
< 5.1.4
5.1.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/tinymce/tinymce/security/advisories/GHSA-27gm-ghr9-4v95
NVD — CVE-2020-17480 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-17480
Tinymce Source Repository REPOSITORY
https://github.com/tinymce/tinymce
portswigger.net/daily-swig/xss-vuln... WEB
https://portswigger.net/daily-swig/xss-vulnerability-patched-in-tinymce
www.tiny.cloud/docs/release-notes/... WEB
https://www.tiny.cloud/docs/release-notes/release-notes514/#securityfixes

Frequently Asked Questions

What is CVE-2020-17480?
CVE-2020-17480 is a security vulnerability in Tinymce involving Cross-site scripting vulnerability in TinyMCE under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Tinymce versions are affected?
Affected versions include releases prior to 4.9.7, 5.1.4 across affected packages: tinymce.
What version fixes CVE-2020-17480?
Upgrading to 4.9.7, 5.1.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tinymce affected?
Yes, tinymce is affected in releases prior to 4.9.7, 5.1.4. Upgrade your dependency to 4.9.7, 5.1.4 or later.
What CWE is associated with CVE-2020-17480?
CVE-2020-17480 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 npm dependencies for CVE-2020-17480?
Run the dependency tree command: 'npm ls tinymce'. 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-27gm-ghr9-4v95",
  "modified" : "2023-06-27T16:50:58Z",
  "published" : "2020-01-30T21:22:15Z",
  "aliases" : [ "CVE-2020-17480" ],
  "summary" : "Cross-site scripting vulnerability in TinyMCE",
  "details" : "### Impact\nA cross-site scripting (XSS) vulnerability was discovered in: the core parser, `paste` and `visualchars` plugins. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor via the clipboard or APIs. This impacts all users who are using TinyMCE 4.9.6 or lower and TinyMCE 5.1.3 or lower.\n\n### Patches\nThis vulnerability has been patched in TinyMCE 4.9.7 and 5.1.4 by improved parser logic and HTML sanitization.\n\n### Workarounds\nThe workarounds available are:\n- disable the impacted plugins\n- manually sanitize the content using the `BeforeSetContent` event (see below)\n- upgrade to either TinyMCE 4.9.7 or TinyMCE 5.1.4\n\n#### Example: Manually sanitize content\n```js\neditor.on('BeforeSetContent', function(e) {\n  var sanitizedContent = ...; // Manually sanitize content here\n  e.content = sanitizedContent;\n});\n```\n\n### Acknowledgements\nTiny Technologies would like to thank Michał Bentkowski for discovering this vulnerability.\n\n### References\nhttps://www.tiny.cloud/docs/release-notes/release-notes514/#securityfixes\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in the [TinyMCE repo](https://github.com/tinymce/tinymce/issues)\n* Email us at [infosec@tiny.cloud](mailto:infosec@tiny.cloud)\n",
  "severity" : [ ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "tinymce"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.9.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "tinymce"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.0.0"
      }, {
        "fixed" : "5.1.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/tinymce/tinymce/security/advisories/GHSA-27gm-ghr9-4v95"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-17480"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tinymce/tinymce"
  }, {
    "type" : "WEB",
    "url" : "https://portswigger.net/daily-swig/xss-vulnerability-patched-in-tinymce"
  }, {
    "type" : "WEB",
    "url" : "https://www.tiny.cloud/docs/release-notes/release-notes514/#securityfixes"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-01-30T19:38:09Z",
    "nvd_published_at" : null
  }
}