# CVE-2020-6809: Firefox ESR: When a Web Extension had the all-urls permission and made a fetch request with a mode set to 'same-origin',…

CVE-2020-6809 is fixed in 4 products on 2 platforms, first by firefox 74.0+build3-0ubuntu0.18.04.1, released March 10, 2020. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2020-6809
- Priority: High
- CVSS: 7.5 (Medium)
- EPSS: 0.0148
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 9, 2020
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2020-6809

## Description

When a Web Extension had the all-urls permission and made a fetch request with a mode set to 'same-origin', it was possible for the Web Extension to read local files. This vulnerability affects Firefox < 74.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 78.0esr | [Mozilla Firefox ESR (en-US) 78.0esr](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-78.0esr.md) | Jun 25, 2020 |
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 74.0+build3-0ubuntu0.18.04.1 | [firefox 74.0+build3-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-74.0-build3-0ubuntu0.18.04.1.md) | Mar 10, 2020 |
| Linux | firefox Ubuntu 20.04 LTS (focal) | 74.0+build3-0ubuntu1 | [firefox 74.0+build3-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-74.0-build3-0ubuntu1.md) | Mar 10, 2020 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 74.0+build3-0ubuntu0.18.04.1 | [firefox-geckodriver 74.0+build3-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-74.0-build3-0ubuntu0.18.04.1.md) | Mar 10, 2020 |
| Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 74.0+build3-0ubuntu1 | [firefox-geckodriver 74.0+build3-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-74.0-build3-0ubuntu1.md) | Mar 10, 2020 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 74.0+build3-0ubuntu0.18.04.1 | [firefox-mozsymbols 74.0+build3-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-74.0-build3-0ubuntu0.18.04.1.md) | Mar 10, 2020 |
| Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 74.0+build3-0ubuntu1 | [firefox-mozsymbols 74.0+build3-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-74.0-build3-0ubuntu1.md) | Mar 10, 2020 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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