Mozilla Foundation Security Advisory 2021-49

Security Vulnerabilities fixed in Firefox ESR 91.3

Announced
November 2, 2021
Impact
high
Products
Firefox ESR
Fixed in
  • Firefox ESR 91.3

#CVE-2021-38503: iframe sandbox rules did not apply to XSLT stylesheets

Reporter
Armin Ebert
Impact
high
Description

The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass restrictions such as executing scripts or navigating the top-level frame.

References

#CVE-2021-38504: Use-after-free in file picker dialog

Reporter
Irvan Kurniawan
Impact
high
Description

When interacting with an HTML input element's file picker dialog with webkitdirectory set, a use-after-free could have resulted, leading to memory corruption and a potentially exploitable crash.

References

#CVE-2021-38505: Windows 10 Cloud Clipboard may have recorded sensitive user data

Reporter
Sergey Galich
Impact
high
Description

Microsoft introduced a new feature in Windows 10 known as Cloud Clipboard which, if enabled, will record data copied to the clipboard to the cloud, and make it available on other computers in certain scenarios. Applications that wish to prevent copied data from being recorded in Cloud History must use specific clipboard formats; and Firefox before versions 94 and ESR 91.3 did not implement them. This could have caused sensitive data to be recorded to a user's Microsoft account.
This bug only affects Firefox for Windows 10+ with Cloud Clipboard enabled. Other operating systems are unaffected.

References

#CVE-2021-38506: Firefox could be coaxed into going into fullscreen mode without notification or warning

Reporter
Irvan Kurniawan
Impact
high
Description

Through a series of navigations, Firefox could have entered fullscreen mode without notification or warning to the user. This could lead to spoofing attacks on the browser UI including phishing.

References

#CVE-2021-38507: Opportunistic Encryption in HTTP2 could be used to bypass the Same-Origin-Policy on services hosted on other ports

Reporter
Takeshi Terada
Impact
high
Description

The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded to TLS while retaining the visual properties of an HTTP connection, including being same-origin with unencrypted connections on port 80. However, if a second encrypted port on the same IP address (e.g. port 8443) did not opt-in to opportunistic encryption; a network attacker could forward a connection from the browser to port 443 to port 8443, causing the browser to treat the content of port 8443 as same-origin with HTTP. This was resolved by disabling the Opportunistic Encryption feature, which had low usage.

References

#MOZ-2021-0008: Use-after-free in HTTP2 Session object

Reporter
Julien Cristau
Impact
high
Description

A use-after-free could have occured when an HTTP2 session object was released on a different thread, leading to memory corruption and a potentially exploitable crash.
Note: This issue is pending a CVE assignment and will be updated when available.

References

#CVE-2021-38508: Permission Prompt could be overlaid, resulting in user confusion and potential spoofing

Reporter
Raphael
Impact
moderate
Description

By displaying a form validity message in the correct location at the same time as a permission prompt (such as for geolocation), the validity message could have obscured the prompt, resulting in the user potentially being tricked into granting the permission.

References

#CVE-2021-38509: Javascript alert box could have been spoofed onto an arbitrary domain

Reporter
Ademar Nowasky Junior
Impact
moderate
Description

Due to an unusual sequence of attacker-controlled events, a Javascript alert() dialog with arbitrary (although unstyled) contents could be displayed over top an uncontrolled webpage of the attacker's choosing.

References

#CVE-2021-38510: Download Protections were bypassed by .inetloc files on Mac OS

Reporter
Hou JingYi
Impact
moderate
Description

The executable file warning was not presented when downloading .inetloc files, which, due to a flaw in Mac OS, can run commands on a user's computer.
Note: This issue only affected Mac OS operating systems. Other operating systems are unaffected.

References

#MOZ-2021-0007: Memory safety bugs fixed in Firefox 94 and Firefox ESR 91.3

Reporter
Mozilla developers
Impact
high
Description

Mozilla developers and community members Christian Holler, Valentin Gosu, and Andrew McCreight reported memory safety bugs present in Firefox 93 and Firefox ESR 91.2. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.
Note: This issue is pending a CVE assignment and will be updated when available.

References