# Firefox Developer Edition (en-US) 139.0

Firefox Developer Edition (en-US) 139.0, released May 18, 2025, fixes 11 CVEs in Firefox Developer Edition (en-US). None of them is reported as exploited. Patch Radar priority: High. The latest Firefox Developer Edition (en-US) is 156.0, which also fixes every one of these CVEs.

- Web page: https://patchblox.com/security/fix/windows-app/mozilla.firefox.developeredition-139.0
- Platform: Windows apps
- Released: May 18, 2025
- Priority: High (Closes CVE-2025-4918, high severity)
- CVEs: 11, exploited: 0, on CISA KEV: 0
- Superseded by: [Firefox Developer Edition (en-US) 156.0](https://patchblox.com/security/data/product/windows-app/firefox-developer-edition-en-us.md), the latest version, which also fixes every CVE listed here

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Firefox Developer Edition (en-US)](https://patchblox.com/security/data/product/windows-app/firefox-developer-edition-en-us.md) |  | 139.0 |

## CVEs this fix closes

| CVE | Priority | Title | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2025-4918](https://patchblox.com/security/data/cve/CVE-2025-4918.md) | High | Out-of-bounds access when resolving Promise objects | 9.8 | 0.0952 |  |
| [CVE-2025-4919](https://patchblox.com/security/data/cve/CVE-2025-4919.md) | High | Out-of-bounds access when optimizing linear sums | 8.8 | 0.0912 |  |
| [CVE-2025-5268](https://patchblox.com/security/data/cve/CVE-2025-5268.md) | High | Memory safety bugs fixed in Firefox 139, Thunderbird 139, Firefox ESR 128.11, and Thunderbird 128.11 | 8.8 | 0.0051 |  |
| [CVE-2025-5266](https://patchblox.com/security/data/cve/CVE-2025-5266.md) | High | Script element events leaked cross-origin resource status | 8.8 | 0.0034 |  |
| [CVE-2025-5272](https://patchblox.com/security/data/cve/CVE-2025-5272.md) | High | Memory safety bugs fixed in Firefox 139 and Thunderbird 139 | 7.3 | 0.0034 |  |
| [CVE-2025-5264](https://patchblox.com/security/data/cve/CVE-2025-5264.md) | High | Potential local code execution in “Copy as cURL” command | 8.8 | 0.0030 |  |
| [CVE-2025-5270](https://patchblox.com/security/data/cve/CVE-2025-5270.md) | High | SNI was sometimes unencrypted | 7.5 | 0.0029 |  |
| [CVE-2025-5267](https://patchblox.com/security/data/cve/CVE-2025-5267.md) | High | Clickjacking vulnerability could have led to leaking saved payment card details | 8.8 | 0.0028 |  |
| [CVE-2025-5263](https://patchblox.com/security/data/cve/CVE-2025-5263.md) | High | Error handling for script execution was incorrectly isolated from web content | 8.8 | 0.0027 |  |
| [CVE-2025-5271](https://patchblox.com/security/data/cve/CVE-2025-5271.md) | Routine | Devtools' preview ignored CSP headers | 6.5 | 0.0030 |  |
| [CVE-2025-5265](https://patchblox.com/security/data/cve/CVE-2025-5265.md) | Routine | Potential local code execution in “Copy as cURL” command | 4.8 | 0.0021 |  |

---

Data as of 2026-11-08T13:06:02Z 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

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.