fix: validate host_url to prevent Host-header injection XSS

[Joshua-Medvinsky]

Summary

The Flask request object is passed as a template variable into render_template_string. The template renders {{ request.host_url }} unescaped. An attacker controlling the Host header can inject arbitrary HTML/JavaScript into the rendered page, achieving XSS against any user visiting the agent UI.

Fix

Do not pass the raw request object into the template. Instead, validate host_url with a regex and pass only the sanitized value. Template updated to use {{ host_url }} instead of {{ request.host_url }}.

Test Plan

• Normal Host header renders correctly
• Injected Host header with <script> tags is sanitized
• All agent UI pages render without XSS

Security Note

Severity: High. Host-header injection → reflected XSS on the trusted origin.

[failsafesecurity]

Hi maintainers — friendly follow-up on this security hardening PR. It has been open for a while with no reviewer feedback, so I wanted to resurface it.

Happy to rebase, adjust the approach, add tests, or split the change differently if that would make review easier. Thanks!

[failsafesecurity]

Hi — this security PR has been open for 40 days without maintainer response. Per our responsible disclosure policy, I'll be closing this PR shortly. I may resubmit via a bounty platform if appropriate. Thanks for your time.

[failsafesecurity]

Closing per responsible disclosure policy: 35+ days open with no maintainer response. May resubmit via bounty platform.

[failsafesecurity]

This security fix has been open for 30+ days. Per our responsible disclosure timeline, we'd like to move toward resolution. We can: (1) rebase and adjust the patch, (2) reach out via security@ email, or (3) resubmit via a bounty platform. Please let us know your preference.