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.
Superseded. The latest Firefox Developer Edition (en-US) is 156.0, which also fixes every CVE on this page. Install that instead.
Priority of the 11 CVEs
Applies to
| Product | Version |
|---|---|
| Firefox Developer Edition (en-US) | 139.0 |
CVEs this fix closes
| Priority | CVE | Title | CVSS | EPSS | Exploitation |
|---|---|---|---|---|---|
| High | CVE-2025-4918 | Out-of-bounds access when resolving Promise objects | 9.8 | 0.0952 | None reported |
| High | CVE-2025-4919 | Out-of-bounds access when optimizing linear sums | 8.8 | 0.0912 | None reported |
| High | CVE-2025-5268 | Memory safety bugs fixed in Firefox 139, Thunderbird 139, Firefox ESR 128.11, and Thunderbird 128.11 | 8.8 | 0.0051 | None reported |
| High | CVE-2025-5266 | Script element events leaked cross-origin resource status | 8.8 | 0.0034 | None reported |
| High | CVE-2025-5272 | Memory safety bugs fixed in Firefox 139 and Thunderbird 139 | 7.3 | 0.0034 | None reported |
| High | CVE-2025-5264 | Potential local code execution in “Copy as cURL” command | 8.8 | 0.0030 | None reported |
| High | CVE-2025-5270 | SNI was sometimes unencrypted | 7.5 | 0.0029 | None reported |
| High | CVE-2025-5267 | Clickjacking vulnerability could have led to leaking saved payment card details | 8.8 | 0.0028 | None reported |
| High | CVE-2025-5263 | Error handling for script execution was incorrectly isolated from web content | 8.8 | 0.0027 | None reported |
| Routine | CVE-2025-5271 | Devtools' preview ignored CSP headers | 6.5 | 0.0030 | None reported |
| Routine | CVE-2025-5265 | Potential local code execution in “Copy as cURL” command | 4.8 | 0.0021 | None reported |
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