fix(core): escape Telegram HTML output (#72)

src/bot/services/ai/telegram_html.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from html import escape
 import re
 
 _BOLD_RE = re.compile(r"\*\*(.+?)\*\*")
@@ -15,7 +16,7 @@ def normalize_llm_output_for_telegram_html(text: str) -> str:
     lines = text.splitlines()
     normalized_lines: list[str] = []
     for line in lines:
-        normalized_lines.append(_BULLET_RE.sub("• ", line))
+        normalized_lines.append(_BULLET_RE.sub("• ", escape(line, quote=False)))
 
     normalized = "\n".join(normalized_lines)
     normalized = _BOLD_RE.sub(r"<b>\1</b>", normalized)

tests/test_telegram_html.py

@@ -13,3 +13,15 @@ def test_markdown_bullets_to_dot_bullets() -> None:
     text = "- first\n* second\n  - third"
     out = normalize_llm_output_for_telegram_html(text)
     assert out.splitlines() == ["• first", "• second", "• third"]
+
+
+def test_escapes_raw_html_control_characters() -> None:
+    text = "Use x < y && y > 0 in <script>alert(1)</script>."
+    out = normalize_llm_output_for_telegram_html(text)
+    assert out == "Use x &lt; y &amp;&amp; y &gt; 0 in &lt;script&gt;alert(1)&lt;/script&gt;."
+
+
+def test_markdown_formatting_escapes_inner_html() -> None:
+    text = "**x < y** and `a & b`"
+    out = normalize_llm_output_for_telegram_html(text)
+    assert out == "<b>x &lt; y</b> and <code>a &amp; b</code>"