Description

A security vulnerability has been detected in Toggl OÜ Toggl Track Extension 4.11.16. This affects an unknown function of the component postMessage Handler. The manipulation leads to origin validation error. It is possible to initiate the attack remotely. The exploit has been disclosed publicly and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.4",
  "pubDate": "2026-08-31T18:17:23.937Z",
  "pubdate": "2026-08-31T18:17:23.937Z",
  "executiveSummary": "A critical security vulnerability has been identified in the Toggl Track Extension version 4.11.16, specifically involving the postMessage handler component. The vulnerability is characterized as an origin validation error, which allows remote attackers to interact with the extension's internal messaging system.\nBy failing to properly verify the origin of incoming postMessage events, the extension exposes itself to unauthorized cross-origin communication. This flaw facilitates potential remote exploitation, as malicious websites or contexts can send spoofed messages to the extension, triggering internal functions.\nThe risk implication is significant, as improper handling of cross-origin messages can lead to unauthorized actions, data leakage, or the execution of unintended operations within the browser extension's context. Because this exploit has been disclosed publicly and the vendor has remained unresponsive, the attack surface remains active for users of the specified version. No authentication is required to initiate an attack, as the vulnerability is inherent to the listener's logic rather than user-provided credentials.",
  "technicalDetails": "The vulnerability resides within the postMessage handler component of the Toggl Track Extension 4.11.16. Browser extensions often utilize the postMessage API to facilitate communication between different windows, iframes, or the background script and content scripts. The root cause of this vulnerability is an insecure implementation of event listener logic that fails to validate the 'origin' property of incoming MessageEvent objects.\nIn a secure implementation, the receiver of a postMessage must explicitly check if the 'event.origin' matches a trusted, hard-coded allowlist of origins. In the case of Toggl Track 4.11.16, the listener accepts messages from any origin without performing this critical verification check. This allows a malicious web page to craft and dispatch arbitrary messages directly to the extension's event handler.\nThe attack flow proceeds as follows: First, an attacker lures a user to a malicious domain. Second, the malicious domain executes a script that calls 'window.postMessage()' targeting the extension. Since the extension's handler lacks origin verification, it processes the attacker-supplied data as if it originated from a trusted source. Third, the internal function invoked by the handler executes the attacker's payload. Depending on the exposed functionality within the handler, this could result in unauthorized modification of user data, the theft of session identifiers, or the execution of arbitrary actions within the Toggl Track interface.\nBecause the extension operates within a privileged browser context, successful exploitation allows the attacker to bypass the Same-Origin Policy (SOP). This grants the attacker the ability to interact with the extension's functionality as if they were a legitimate user or a trusted internal component. The impact is elevated by the fact that the exploit is disclosed and readily available for malicious actors. No specific privilege levels are required for the attacker; the vulnerability is exposed via the browser's document object model, making it reachable from any reachable web context."
}