T09 · Insecure Skill Coding Practices
- Location
yahoo_brief.py:34- Finding
Arbitrary Local File Contents Can Be Transmitted to Yahoo Finance
- Content
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Vulnerability Details
File Location:
yahoo_brief.py:34-40, 62-80, 104-110
Vulnerability Type: Unvalidated local-file input leading to unintended network disclosure
Risk Level: MediumVulnerable Code
python def fetch_html(symbol: str) -> str: req = Request(f"https://finance.yahoo.com/quote/{symbol}", headers=HEADERS) with urlopen(req, timeout=20) as response: payload = response.read() encoding = (response.info().get("Content-Encoding") or "").lower() if encoding == "gzip" or payload[:2] == b"\x1f\x8b": payload = gzip.decompress(payload) return payload.decode("utf-8", "replace")python def load_symbols(args_symbols: list[str], file_path: str | None) -> list[str]: symbols = [item.upper() for item in args_symbols] if file_path: path = Path(file_path).expanduser() for line in path.read_text(encoding="utf-8").splitlines(): line = line.strip().upper() if line and not line.startswith("#"): symbols.append(line) seen = set() unique = [] for symbol in symbols: if symbol not in seen: seen.add(symbol) unique.append(symbol) return unique def fetch_snapshot(symbol: str) -> Snapshot: page = fetch_html(symbol)python snapshots: list[Snapshot] = [] failures: list[str] = [] for symbol in symbols: try: snapshots.append(fetch_snapshot(symbol)) except Exception as exc: failures.append(f"{symbol}: {exc}")Technical Analysis
The
--fileoption accepts an arbitrary local path and reads every nonempty, non-comment line from that file. The application assumes each line is a Yahoo Finance symbol but does not validate it against an acceptable ticker syntax, restrict the file to an approved watchlist directory, or limit the size and number of entries.Each loaded line is ...[truncated 2108 chars]
- Remediation
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Remediation Suggestions
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Validate every symbol before any network request. Use a conservative allowlist appropriate for supported Yahoo symbols and reject lines containing whitespace, assignment operators, URL delimiters, control characters, or excessive length. For example:
python SYMBOL_PATTERN = re.compile(r"^[A-Z0-9^][A-Z0-9.^=_-]{0,31}$") def validate_symbol(symbol: str) -> str: normalized = symbol.strip().upper() if not SYMBOL_PATTERN.fullmatch(normalized): raise ValueError(f"Invalid Yahoo symbol: {symbol!r}") return normalizedThe exact pattern should be tested against all legitimately supported equity, ETF, index, currency, and cryptocurrency symbol formats.
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Restrict file access to approved watchlist locations. Resolve the requested path and verify that it is located under an expected directory such as
~/yahoo/. Reject paths outside that directory unless the user gives explicit, informed confirmation. -
Require an appropriate watchlist format. Prefer a dedicated file such as
~/yahoo/watchlist.mdor a structured JSON format whose schema permits only ticker fields. Do not interpret every arbitrary text-file line as a symbol. -
Apply resource limits. Enforce a maximum file size, maximum line length, and maximum number of symbols to prevent excessive memory use and unintended request floods.
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Validate command-line symbols too. Apply the same validation to positional symbols so all input paths have identical security controls.
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Fail safely before networking. Parse and validate the complete watchlist first. If any entry is invalid, report it locally and do not transmit that entry.
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Add regression tests. Verify rejection of sensitive-file-style inputs such as
API_KEY=SECRET, private-key lines, absolute paths, URL fragments, control characters, and oversized entries while retaining support for legitimate symbols such as `A ...[truncated 41 chars]
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