Impact
When displaying messages with embedded remote images, Zulip normally loads the image preview via a go-camo proxy server. However, an attacker who can send messages could include a crafted URL that tricks the server into embedding a remote image reference directly. This could allow the attacker to infer the viewer’s IP address and browser fingerprinting information.
Patches
This vulnerability is fixed in Zulip Server 5.6.
Workarounds
Zulip organizations with image and link previews disabled are not affected.
References
https://blog.zulip.com/2022/08/24/zulip-server-5-6-security-release/
For more information
If you have any questions or comments about this advisory, you can discuss them on the developer community Zulip server, or email the Zulip security team.
Impact
When displaying messages with embedded remote images, Zulip normally loads the image preview via a go-camo proxy server. However, an attacker who can send messages could include a crafted URL that tricks the server into embedding a remote image reference directly. This could allow the attacker to infer the viewer’s IP address and browser fingerprinting information.
Patches
This vulnerability is fixed in Zulip Server 5.6.
Workarounds
Zulip organizations with image and link previews disabled are not affected.
References
https://blog.zulip.com/2022/08/24/zulip-server-5-6-security-release/
For more information
If you have any questions or comments about this advisory, you can discuss them on the developer community Zulip server, or email the Zulip security team.