When a HTTPS pages was embedded in a HTTP page, and there was a service worker registered for the former, the service worker could have intercepted the request for the secure page despite the iframe not being a secure context due to the (insecure) framing. This vulnerability affects Firefox < 84.
https://bugzilla.mozilla.org/show_bug.cgi?id=1674343
https://lists.debian.org/debian-lts-announce/2021/02/msg00001.html
https://lists.debian.org/debian-lts-announce/2021/02/msg00002.html
https://security.gentoo.org/glsa/202102-02
https://www.debian.org/security/2021/dsa-4840
Source: MITRE
Published: 2021-01-07
Updated: 2021-02-15
Type: NVD-CWE-noinfo
Base Score: 4.3
Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N
Impact Score: 2.9
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 6.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Impact Score: 3.6
Exploitability Score: 2.8
Severity: MEDIUM