The implementation of backslash parsing in the Dart URI class for versions prior to 2.18 and Flutter versions prior to 3.30 differs from the WhatWG URL standards. Dart uses the RFC 3986 syntax, which creates incompatibilities with the '\' characters in URIs, which can lead to auth bypass in webapps interpreting URIs. We recommend updating Dart or Flutter to mitigate the issue.
Dart SDK contains the HTTPClient in dart:io library whcih includes authorization headers when handling cross origin redirects. These headers may be explicitly set and contain sensitive information. By default, HttpClient handles redirection logic. If a request is sent to example.com with authorization header and it redirects to an attackers site, they might not expect attacker site to receive authorization header. We recommend updating the Dart SDK to version 2.16.0 or beyond.