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Apple Safari Security Feature Bypass (Trusted Downloads)

Low

Synopsis

A flaw exists in the Safari browser that allows for the bypass of a security mechanism.

The Safari browser on macOS has a "Trusted Downloads" security feature that, by default, requires downloads from websites to be approved by the end user before that domain is allowed to download the remote resource. The feature being referred to is referenced under the "Downloads" heading here: https://support.apple.com/guide/safari/websites-ibrwe2159f50/mac

This feature appears to key off the domain of the currently loaded page rather than the domain of the remote resource itself, which allows a malicious actor to abuse site-redirects and cause downloads to appear to come from a trusted domain.

For example, redirects from Youtube follow the following format: https://www.youtube.com/redirect?event=video_description&q=<website to redirect to>

If you were to visit: https://www.youtube.com/redirect?event=video_description&q=https://releases.ubuntu.com/22.04/ubuntu-22.04-desktop-amd64.iso and click the "go to site" link, it'll initially prompt you to trust "youtube.com" for downloads, despite the fact that the download comes from ubuntu.com. If you visit the link again, for anything in the "q=" field for any download you want, you won't get the prompt because youtube.com is trusted.  For example, subsequently visiting https://www.youtube.com/redirect?event=video_description&q=https://download.fedoraproject.org/pub/fedora/linux/releases/36/Workstation/x86_64/iso/Fedora-Workstation-Live-x86_64-36-1.5.iso will allow the download even if "fedoraproject.org" is not trusted. This download will occur even if "fedoraproject.org" is specifically untrusted.

Solution

Apple has stated that they do not see any security implications with regards to this flaw and as such, have not provided a patch.

Disclosure Timeline

June 8, 2022 - Tenable discloses to Apple.
June 8, 2022 - Apple provides automated acknowledgement.
June 9, 2022 - Apple provides formal acknowledgement.
June 28, 2022 - Tenable requests status update.
June 28, 2022 - Apple states that they see no security implications with regards to the reported flaw.
June 28, 2022 - Tenable acknowledges Apple's response and sends advisory link.

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

Risk Information

Tenable Advisory ID: TRA-2022-24
CVSSv3 Base / Temporal Score:
3.1 / 3.1
CVSSv3 Vector:
AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N
Risk Factor:
Low

Advisory Timeline

June 28, 2022 - Initial release