fix(examples): base64-encode HTML in site-to-markdown to prevent f-string injection#179
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The site-to-markdown example interpolates scraped page HTML directly
into the generated Jupyter code inside triple-quoted strings:
code=f\"\"\"
html = '''{html}'''
...
\"\"\"
Any page whose HTML contains \`'''\` (unlikely but possible) or a
backslash sequence would break out of the string literal and either
produce a SyntaxError or, in the worst case, execute attacker-chosen
Python in the sandbox. Since the sandbox is the same one the user is
running other code in, this is more than cosmetic.
Base64-encode the HTML on the host side and decode it inside the
sandbox so only 7-bit-safe ASCII crosses the f-string boundary.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Fixes #178.
The
site-to-markdownexample interpolated scraped HTML directly into an f-string containing an inner triple-quoted literal. Pages whose content includes'''(or stray backslashes) break out of the string, producing either a SyntaxError or arbitrary Python execution in the sandbox.Fix: base64-encode the HTML on the host and decode it inside the sandbox. Only ASCII alphanumerics and
+/=cross the f-string boundary, so no page content can alter the generated Python source.Test plan
'''in the body — previously raised SyntaxError, now runs cleanly and produces correct markdown.Related
Part of splitting closed PR #167 into focused single-bug PRs. Previously opened: #171 (Bug 1), #173 (Bug 2), #175 (Bug 3), #177 (Bug 4). This is Bug 5.
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