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🛡️ Sentinel: [HIGH] Fix HTML comment breakout in JSON serialization #6

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github-actions merged 1 commit into from
Jun 20, 2026
Merged

🛡️ Sentinel: [HIGH] Fix HTML comment breakout in JSON serialization #6

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4 changes: 4 additions & 0 deletions .jules/sentinel.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
## 2024-06-20 - Prevent HTML Comment Breakout in JSON Serialization
**Vulnerability:** Markdown Injection / HTML Comment Breakout
**Learning:** JSON serialized into HTML comments (like `<!-- json -->`) can contain `-->` in string values, causing GitHub's Markdown parser to close the comment prematurely and render the remaining JSON as attacker-controlled text or Markdown.
**Prevention:** Always escape `<` and `>` as `\u003c` and `\u003e` (and `&` as `\u0026`) when embedding JSON in HTML contexts (even Markdown comments) to prevent breakout.
1 change: 1 addition & 0 deletions scripts/ci/opencode_review_normalize_output.py
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Expand Up @@ -123,6 +123,7 @@ def main(argv: list[str]) -> int:
continue

normalized_json = json.dumps(control, separators=(",", ":"), ensure_ascii=False)
normalized_json = normalized_json.replace("<", "\\u003c").replace(">", "\\u003e").replace("&", "\\u0026")
output_file.write_text(
"\n".join(
[
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