GHSA-QQ9G-96V4-M3CJ

The Select schema plugin in @pdfme/schemas constructs HTML from template-defined option values using unsanitized string interpolation and sets it via innerHTML, enabling arbitrary JavaScript execution.

Details

In packages/schemas/src/select/index.ts, lines 159-164, the Select schema's ui renderer builds <option> elements by directly interpolating option values from the template into an HTML string:

const options = Array.isArray(schema.options) ? schema.options : [];
selectElement.innerHTML = options
  .map(
    (option) =>
      `<option value="${option}" ${option === value ? 'selected' : ''}>${option}</option>`,
  )
  .join('');

The option values come from schema.options, which is an array of strings defined in the template JSON. These values are interpolated directly into the HTML string without any escaping of <, >, ", &, or other HTML-special characters. An option value containing "> breaks out of the value attribute and allows injection of arbitrary HTML elements and event handlers.

Proof of Concept

Loading the following template into a pdfme Form or Designer component triggers JavaScript execution:

{
  "basePdf": { "width": 210, "height": 297, "padding": [20, 20, 20, 20] },
  "schemas": [[
    {
      "name": "malicious_select",
      "type": "select",
      "content": "Normal",
      "options": [
        "Normal",
        "\"></option><img src=x onerror=\"alert(document.domain)\">"
      ],
      "position": { "x": 20, "y": 20 },
      "width": 80,
      "height": 10
    }
  ]]
}

The injected <img onerror> element executes JavaScript because it is parsed as HTML when assigned to selectElement.innerHTML.

Attack Vectors

The options array is defined in the template (not by form-filling end users). The attack requires a malicious template to be loaded, which can happen via:

1. File upload (e.g., "Load Template" functionality in applications)
2. Shared/imported templates in multi-tenant applications
3. Templates stored in databases without content sanitization
4. The updateTemplate() API being called with untrusted data

This vulnerability is triggered in Form mode (for non-readOnly select fields) and Designer mode when the select element is rendered.

An attacker who can supply a malicious template can execute arbitrary JavaScript in the browser of any user who views or interacts with the template. This enables:

• Session hijacking via cookie/token theft
• Keylogging of form input data
• Phishing and page modification
• Data exfiltration

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

GHSA-QQ9G-96V4-M3CJ has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.5.9); upgrading removes the vulnerable code path.

Kodem intelligence

Use DOM APIs to create option elements safely instead of string interpolation:

options.forEach((option) => {
  const optionEl = document.createElement('option');
  optionEl.value = option;
  optionEl.textContent = option;
  if (option === value) optionEl.selected = true;
  selectElement.appendChild(optionEl);
});

Alternatively, HTML-encode option values before interpolation:

const escape = (s) => s.replace(/&/g, '&amp;').replace(/"/g, '&quot;').replace(/</g, '&lt;').replace(/>/g, '&gt;');

1. What is GHSA-QQ9G-96V4-M3CJ? GHSA-QQ9G-96V4-M3CJ is a medium-severity cross-site scripting (XSS) vulnerability in @pdfme/schemas (npm), affecting versions <= 5.5.8. It is fixed in 5.5.9. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is GHSA-QQ9G-96V4-M3CJ? GHSA-QQ9G-96V4-M3CJ has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @pdfme/schemas are affected by GHSA-QQ9G-96V4-M3CJ? @pdfme/schemas (npm) versions <= 5.5.8 is affected.
4. Is there a fix for GHSA-QQ9G-96V4-M3CJ? Yes. GHSA-QQ9G-96V4-M3CJ is fixed in 5.5.9. Upgrade to this version or later.
5. Is GHSA-QQ9G-96V4-M3CJ exploitable, and should I be worried? Whether GHSA-QQ9G-96V4-M3CJ is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-QQ9G-96V4-M3CJ is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-QQ9G-96V4-M3CJ? Upgrade @pdfme/schemas to 5.5.9 or later.