Quick answers
- Is CVE-2026-100823 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-100823 being exploited in the wild.
- How severe is CVE-2026-100823?
- Informational severity, published 29 September 2026.
- Which products and versions are affected?
- Mozilla Firefox for Android before 157.
- Is there a fix for CVE-2026-100823?
- A patch was published on 2026-09-29: Firefox 157 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-100823 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-100823?
- Check whether you run Mozilla Firefox for Android at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The Downloads component in Firefox for Android truncates long filenames from the end rather than the middle, which removes the file extension from the download completion notification. This is a spoofing vulnerability that allows file type confusion—an attacker can host a malicious executable (e.g., .exe or .apk) with a long filename prefix that appears harmless in the truncated notification. The issue was resolved in Firefox 157 by implementing truncation in the middle of the filename.
Affected products
- Mozilla Firefox for Android before 157
Timeline
- 2026-09-29: disclosed
- 2026-09-29: patched: Firefox 157