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Sanitize request.url_root to prevent Host header injection in documentation route #51

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Sanitize request.url_root to prevent Host header injection in documentation route #51

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Copilot Mar 6, 2026
778ba8e
Sanitize request.url_root to prevent Host header injection
Copilot Mar 6, 2026
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12 changes: 9 additions & 3 deletions app/routes.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
import markdown
from flask import Blueprint, current_app, jsonify, make_response, redirect, request, url_for
from markupsafe import Markup
from urllib.parse import urlparse
from sqlalchemy.orm.exc import NoResultFound

from .models import ZephirFiledata
Expand Down Expand Up @@ -39,12 +40,17 @@ def documentation():
with open('API.md', 'r') as file:
content = file.read()

# Sanitize the URL root by reconstructing it from only the scheme and netloc,
# preventing Host header injection from affecting the rendered output.
parsed = urlparse(request.url_root)
safe_url_root = f"{parsed.scheme}://{parsed.netloc}/"

# Convert Markdown to HTML
html_content = markdown.markdown(content.replace('http://localhost/', request.url_root))
html_content = markdown.markdown(content.replace('http://localhost/', safe_url_root))

# Return HTML content. The Markup class prevents Flask from escaping HTML content.
# Bandit flags this as unsafe, but the markup is entirely within our control so it's safe
return Markup(html_content) # nosec
# The content is safe: it comes from a controlled Markdown file and the URL is sanitized.
return Markup(html_content) # nosec B704


@blueprint.route('/ping')
Expand Down