CVE-2025-8349: Tawk Live Chat Stored XSS Vulnerability

CVE-2025-8349 Overview

CVE-2025-8349 is a stored Cross-Site Scripting (XSS) vulnerability [CWE-79] in Tawk Live Chat. Attackers upload a malicious PDF containing a JavaScript payload through the chatbot file-upload feature. The application stores the PDF and later renders it to other users without sanitisation, executing the embedded JavaScript in their browser context.

Successful exploitation allows attackers to steal session cookies, hijack authenticated sessions, or perform actions on behalf of the victim user. The vulnerability requires user interaction, since a victim must open the stored PDF for the payload to trigger.

Critical Impact
Attackers can execute arbitrary JavaScript in the browser of any user who views the malicious PDF, enabling session theft and unauthorized actions within the Tawk Live Chat context.

Affected Products

Tawk Live Chat (specific version range not published in NVD)
Web applications embedding the Tawk Live Chat widget with file-upload enabled
End-user browsers rendering PDFs served from the Tawk chat interface

Discovery Timeline

2025-10-20 - CVE-2025-8349 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-8349

Vulnerability Analysis

The flaw is a stored XSS delivered through a PDF file upload channel in the Tawk Live Chat product. PDF files support embedded JavaScript through the /JS and /JavaScript action dictionaries defined in the PDF specification. When Tawk Live Chat serves the uploaded PDF back to another user without stripping active content or enforcing a safe content disposition, the browser or embedded PDF viewer executes the attacker-controlled script.

Because the payload is persisted server-side, every subsequent user who views the file is exposed. This makes the issue more damaging than reflected XSS variants, as the attacker does not need to lure each victim individually. The vulnerability is network-reachable and requires no authentication to plant the payload, only interaction from a victim to trigger it.

Root Cause

The root cause is missing output sanitisation and unsafe content handling for user-supplied file uploads. The application accepts PDF attachments through chat, stores them, and returns them to other participants with a content type or inline disposition that permits script execution. No validation strips embedded JavaScript actions from the PDF prior to storage or delivery.

Attack Vector

An unauthenticated attacker initiates a chat session with a target site and uploads a crafted PDF that contains a JavaScript action in its object tree. The PDF is stored on the Tawk backend and referenced in the conversation. When an operator or another user opens the file inline, the PDF viewer executes the JavaScript with access to the surrounding page context, allowing cookie theft or DOM-based actions. Refer to the INCIBE Security Notice on XSS for the coordinated disclosure details.

Detection Methods for CVE-2025-8349

Indicators of Compromise

PDF attachments in Tawk chat sessions containing /JavaScript or /JS action dictionaries or /OpenAction entries referencing script
Outbound requests from operator browsers to unexpected domains immediately after opening a chat-delivered PDF
Session cookies for the Tawk dashboard appearing in web server logs of attacker-controlled infrastructure
Unusual chat sessions from anonymous visitors that upload PDF files with no accompanying legitimate message content

Detection Strategies

Inspect stored PDFs with tools such as pdfid and pdf-parser to flag files containing JavaScript actions before they reach operators.
Monitor Content Security Policy (CSP) violation reports from the chat operator console for blocked inline script executions.
Review web proxy and endpoint telemetry for browser processes spawning network connections to unknown hosts shortly after PDF views.

Monitoring Recommendations

Log all file uploads through the Tawk widget, including uploader IP, file hash, and MIME type, and retain them for retrospective hunting.
Alert on any PDF served from the chat backend that contains active JavaScript objects.
Track anomalous authentication activity on the Tawk operator dashboard, including new sessions from unexpected geolocations following PDF interactions.

How to Mitigate CVE-2025-8349

Immediate Actions Required

Disable PDF uploads in Tawk Live Chat configuration until the vendor provides a fix, or restrict attachments to image formats only.
Force PDF downloads with Content-Disposition: attachment rather than inline rendering so the browser does not execute embedded scripts.
Instruct chat operators to save PDFs locally and open them in a sandboxed viewer with JavaScript disabled.

Patch Information

No vendor patch reference is published in NVD at the time of writing. Monitor the INCIBE advisory and the Tawk vendor communications for a fixed release. Apply the update as soon as it becomes available.

Workarounds

Configure a strict Content Security Policy on pages that embed the Tawk widget to block inline script execution and restrict script sources.
Route attachments through a sanitisation proxy that strips JavaScript actions from PDFs before delivery to operators.
Disable JavaScript in the PDF viewer used by operators (for example, Adobe Reader preferences or browser PDF plugin settings).
Segment the operator dashboard to a dedicated browser profile with no access to sensitive session cookies from other applications.

bash

# Example: strip JavaScript from PDFs using qpdf before storage or delivery
qpdf --object-streams=disable --qdf input.pdf sanitized.pdf
sed -i 's|/JavaScript|/XX|g; s|/JS|/XX|g; s|/OpenAction|/XX|g' sanitized.pdf
qpdf sanitized.pdf final.pdf