Flatpak-builder Path Traversal

Flatpak is a Linux application sandboxing and distribution framework. A path traversal vulnerability affects versions of Flatpak prior to 1.12.3 and 1.10.6. flatpak-builder applies `finish-args` last in the build. At this point the build directory will have the full access that is specified in the manifest, so running `flatpak build` against it will gain those permissions. Normally this will not be done, so this is not problem. However, if `--mirror-screenshots-url` is specified, then flatpak-builder will launch `flatpak build --nofilesystem=host appstream-utils mirror-screenshots` after finalization, which can lead to issues even with the `--nofilesystem=host` protection. In normal use, the only issue is that these empty directories can be created wherever the user has write permissions. However, a malicious application could replace the `appstream-util` binary and potentially do something more hostile. This has been resolved in Flatpak 1.12.3 and 1.10.6 by changing the behaviour of `--nofilesystem=home` and `--nofilesystem=host`. (2022-01-13, CVE-2022-21682)

Relative Path Confusion means that your web server is configured to serve responses to ambiguous URLs. This configuration can possibly cause confusion about the correct relative path for the URL. It is also an issue of resources, such as images, styles etc., which are specified in the response using relative path, not the absolute URL.

If the web browser permits to parse "cross-content" response, the attacker may be able to fool the web browser into interpreting HTML into other content types, which can then lead to a cross site scripting attack (link do XSS).