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8.8
Firefox ESR allows Flash POST redirects to skip cross‑origin checks
published 4 days ago
Summary
Firefox ESR’s support for old plug‑ins like Flash can let a POST request that receives a 308 redirect bypass the usual cross‑origin rules. This means a web page could potentially send data to a different site without the normal protections. Update Firefox ESR to a version that removes this behavior or disable NPAPI plug‑ins such as Flash.
What to do
- Update cleanstart firefox-esr to version 68.0-r0.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| CleanStart | cleanstart | firefox-esr |
< 68.0-r0 Fix: upgrade to 68.0-r0
|
Original advisory text
POST requests made by NPAPI plugins, such as Flash, that receive a status 308 redirect response can bypass CORS requirements
Security vulnerability affects the firefox-esr package. POST requests made by NPAPI plugins, such as Flash, that receive a status 308 redirect response can bypass CORS requirements.
Internet-facing
14 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit (estimated)
- Gives an attacker full control (estimated)
Timeline
Published31 Oct 2026
Updated31 Oct 2026
First seen31 Oct 2026
Sources
CLEANSTART-2024-SO83448 · OSV
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