9.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-31938

CVE-2026-31938: jsPDF has HTML Injection in New Window paths

jsPDF is a library to generate PDFs in JavaScript. Prior to version 4.2.1, user control of the options argument of the output function allows attackers to inject arbitrary HTML (such as scripts) into the browser context the created PDF is opened in. The vulnerability can be exploited in the following scenario: the attacker provides values for the output options, for example via a web interface. These values are then passed unsanitized (automatically or semi-automatically) to the attack victim. The victim creates and opens a PDF with the attack vector using one of the vulnerable method overloads inside their browser. The attacker can thus inject scripts that run in the victims browser context and can extract or modify secrets from this context. The vulnerability has been fixed in jspdf@4.2.1. As a workaround, sanitize user input before passing it to the output method.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-31938

CVE-2026-31938:

9.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
jspdf	npm	<= 4.2.0	4.2.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The analysis of the security advisory and the associated patch commit 87a40bbd07e6b30575196370670b41f264aa78d7 clearly indicates that the vulnerability lies within the output method of the jsPDF object, located in src/jspdf.js. The vulnerability description explicitly names the output function and details how different options (pdfobjectnewwindow, pdfjsnewwindow, dataurlnewwindow) can be exploited.

The patch confirms this by making several key changes inside the output function's implementation:

For the datauristring output type (which is used by dataurlnewwindow), it replaces direct use of options.filename with encodeURIComponent(options.filename). This prevents manipulation of the data URI structure.
For the pdfobjectnewwindow, pdfjsnewwindow, and dataurlnewwindow output types, the patch refactors the code to stop generating raw HTML strings via concatenation (document.write(...)). Instead, it uses the safer DOM API (createElement, setting .src property) to build the content of the new window. This prevents attackers from injecting malicious HTML tags and scripts through the options.

The vulnerable function is identified as jsPDF.output because it is the entry point that processes the malicious input and, prior to the patch, performed the unsafe string concatenations that led to the HTML injection vulnerability.

Vulnerable functions

jsPDF.output

src/jspdf.js

The `output` function is vulnerable to HTML injection. When called with specific `type` arguments (`pdfobjectnewwindow`, `pdfjsnewwindow`, `dataurlnewwindow`), it constructs HTML strings for a new browser window using user-provided options without proper sanitization. For example, with `pdfjsnewwindow`, the `options.filename` is directly concatenated into an iframe's `src` attribute, allowing an attacker to break out of the attribute and inject arbitrary HTML and script content.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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