[Security] Open Redirect vulnerability via double-slash pathname in history v4.x (CVE-2025-68470)

Reproduction

Fork with failing tests: https://github.com/ebsmoove/history/tree/bug-report/v4-open-redirect-cve-2025-68470

Steps to reproduce:

1. Clone the fork: git clone https://github.com/ebsmoove/history.git
2. Checkout branch: git checkout bug-report/v4-open-redirect-cve-2025-68470
3. Install dependencies: npm install
4. Run tests: npm test
5. Observe 8 failing tests demonstrating the open redirect vulnerability

Fix available: https://github.com/remix-run/history/pull/981

System Info

System: OS: macOS 15.6.1 CPU: (12) arm64 Apple M2 Pro Memory: 1.98 GB / 32.00 GB Shell: 5.9 - /bin/zsh Binaries: Node: 22.14.0 - /Users/X/.asdf/installs/nodejs/22.14.0/bin/node npm: 10.9.2 - /Users/X/.asdf/plugins/nodejs/shims/npm

Used Package Manager

npm

Expected Behavior

Pathnames with embedded double-slashes like //evil.com should be normalized to /evil.com to prevent the browser from interpreting them as protocol-relative URLs that redirect to external sites.

Actual Behavior

Pathnames with embedded double-slashes like //evil.com are passed through unchanged, allowing browsers to interpret them as protocol-relative URLs (e.g., https://evil.com), enabling open redirect attacks.