🛡️ Sentinel: [HIGH] Fix Markdown Injection in JSON output

.jules/sentinel.md

@@ -6,3 +6,8 @@
 **Vulnerability:** Workflow CI Security Bypass / Markdown Injection
 **Learning:** The GitHub Actions workflow `opencode-review.yml` attempted to optimize performance by doing a fast-path bash string extraction. If this succeeded, it skipped the Python JSON normalizer (`opencode_review_normalize_output.py`). This is a security flaw because the bash script does not escape `<, >, &` characters, allowing attackers to inject `-->` directly in JSON strings to break out of HTML comment sections.
 **Prevention:** Removed the fast-path check entirely. We must always enforce JSON normalization via `opencode_review_normalize_output.py` because it correctly parses the JSON payload and safely escapes all characters as `\u003c`, `\u003e` and `\u0026`.
+
+## 2025-02-23 - Prevent JSON Markdown Injection in Python Normalizer
+**Vulnerability:** Markdown Injection / HTML Comment Breakout
+**Learning:** `json.dumps()` in python does not automatically escape HTML sensitive characters `<, >, &` into unicode forms. When outputting JSON to an HTML comment format like `<!-- opencode-review-control-v1 { ... } -->`, it is susceptible to breakout.
+**Prevention:** Ensured XSS prevention by chaining `.replace("<", "\\u003c").replace(">", "\\u003e").replace("&", "\\u0026")` to the dumped JSON output in `scripts/ci/opencode_review_normalize_output.py`.

scripts/ci/opencode_review_normalize_output.py

@@ -473,6 +473,11 @@ 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(
                 [

tests/test_opencode_review_normalize_output.py

@@ -368,3 +368,26 @@ def test_main_normalizes_valid_output_and_reports_failures(tmp_path, capsys):
     approval = tmp_path / "approval.json"
     approval.write_text(json.dumps(control()), encoding="utf-8")
     assert norm.main(["prog", "--check-structural-approval", str(approval)]) == 0
+
+def test_main_escapes_html_chars(tmp_path):
+    control_json = {
+        "head_sha": "head",
+        "run_id": "run",
+        "run_attempt": "attempt",
+        "result": "APPROVE",
+        "reason": "Security review\nChanged files\npath.py",
+        "summary": FULL_SUMMARY + "\n<script>alert(1)</script> & -->",
+        "findings": [],
+    }
+    input_text = f"```json\n{json.dumps(control_json)}\n```"
+
+    output_file = tmp_path / "output.md"
+    output_file.write_text(input_text, encoding="utf-8")
+    argv = ["script", "head", "run", "attempt", str(output_file)]
+
+    result = norm.main(argv)
+    assert result == 0
+    output_content = output_file.read_text(encoding="utf-8")
+    assert "<script>" not in output_content
+    assert "\\u003cscript\\u003e" in output_content
+    assert "\\u0026 --\\u003e" in output_content