### [CVE-2021-43536](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-43536)
![](https://img.shields.io/static/v1?label=Product&message=Firefox%20ESR&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=Firefox&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=Thunderbird&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2091.4.0%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2095%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=URL%20leakage%20when%20navigating%20while%20executing%20asynchronous%20function&color=brighgreen)

### Description

Under certain circumstances, asynchronous functions could have caused a navigation to fail but expose the target URL. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.

### POC

#### Reference
- https://bugzilla.mozilla.org/show_bug.cgi?id=1730120

#### Github
No PoCs found on GitHub currently.