security: Apply critical security fixes from PR #281 review

Implement the top 3 critical security fixes identified in Gemini code review:

**Fix 1: ChromaDB Reset Protection**
- Changed `allow_reset=True` to `False` in memory.py
- Prevents catastrophic database deletion in production
- File: tradingagents/agents/utils/memory.py:13

**Fix 2: Path Traversal Prevention**
- Added `validate_ticker_symbol()` function with comprehensive validation
- Applied validation to 5 functions using ticker in file paths:
  - get_YFin_data_window()
  - get_YFin_data()
  - get_data_in_range()
  - get_finnhub_company_insider_sentiment()
  - get_finnhub_company_insider_transactions()
- Blocks: path traversal (../, \\), invalid chars, length > 10
- File: tradingagents/dataflows/local.py

**Fix 3: CLI Input Validation**
- Added validation loop to get_ticker() with user-friendly error messages
- Prevents malicious input at entry point
- Validates format, blocks traversal, limits length
- File: cli/main.py:499-521

**Testing:**
- Validation logic verified with attack vectors:
  - ../../etc/passwd (blocked ✓)
  - Long tickers (blocked ✓)
  - Special characters (blocked ✓)
  - Valid tickers: AAPL, BRK.B (pass ✓)

**Changes:**
- 3 files changed, 65 insertions(+), 3 deletions(-)
- Implementation time: ~20 minutes
- Zero breaking changes to existing functionality

**References:**
- Security analysis: docs/security/PR281_CRITICAL_FIXES.md
- Future roadmap: docs/security/FUTURE_HARDENING.md

Addresses critical path traversal (CWE-22) and data loss vulnerabilities.

cli/main.py

@@ -497,8 +497,28 @@ def get_user_selections():
 
 
 def get_ticker():
-    """Get ticker symbol from user input."""
-    return typer.prompt("", default="SPY")
+    """Get ticker symbol from user input with validation."""
+    while True:
+        ticker = typer.prompt("", default="SPY")
+        try:
+            # Validate ticker format
+            if not ticker or len(ticker) > 10:
+                console.print("[red]Error: Ticker must be 1-10 characters[/red]")
+                continue
+
+            # Check for path traversal attempts
+            if '..' in ticker or '/' in ticker or '\\' in ticker:
+                console.print("[red]Error: Invalid characters in ticker symbol[/red]")
+                continue
+
+            # Validate characters (alphanumeric, dots, hyphens only)
+            if not all(c.isalnum() or c in '.-' for c in ticker):
+                console.print("[red]Error: Ticker can only contain letters, numbers, dots, and hyphens[/red]")
+                continue
+
+            return ticker.upper()  # Return normalized uppercase ticker
+        except Exception as e:
+            console.print(f"[red]Error validating ticker: {e}[/red]")
 
 
 def get_analysis_date():

tradingagents/agents/utils/memory.py

@@ -10,7 +10,7 @@ class FinancialSituationMemory:
         else:
             self.embedding = "text-embedding-3-small"
         self.client = OpenAI(base_url=config["backend_url"])
-        self.chroma_client = chromadb.Client(Settings(allow_reset=True))
+        self.chroma_client = chromadb.Client(Settings(allow_reset=False))
         self.situation_collection = self.chroma_client.create_collection(name=name)
 
     def get_embedding(self, text):

tradingagents/dataflows/local.py

@@ -7,12 +7,45 @@ from dateutil.relativedelta import relativedelta
 import json
 from .reddit_utils import fetch_top_from_category
 from tqdm import tqdm
+import re
+
+
+def validate_ticker_symbol(symbol: str) -> str:
+    """
+    Validate and sanitize ticker symbol to prevent path traversal attacks.
+
+    Args:
+        symbol: Ticker symbol to validate
+
+    Returns:
+        Sanitized ticker symbol (uppercase)
+
+    Raises:
+        ValueError: If ticker contains invalid characters or patterns
+    """
+    # Ticker symbols should only contain alphanumeric characters, dots, and hyphens
+    if not re.match(r'^[A-Za-z0-9.\-]+$', symbol):
+        raise ValueError(f"Invalid ticker symbol: {symbol}")
+
+    # Prevent path traversal patterns
+    if '..' in symbol or '/' in symbol or '\\' in symbol:
+        raise ValueError(f"Path traversal attempt detected in ticker: {symbol}")
+
+    # Limit length (typical tickers are 1-5 characters, extended can be up to 10)
+    if len(symbol) > 10:
+        raise ValueError(f"Ticker symbol too long: {symbol}")
+
+    return symbol.upper()  # Normalize to uppercase
+
 
 def get_YFin_data_window(
     symbol: Annotated[str, "ticker symbol of the company"],
     curr_date: Annotated[str, "Start date in yyyy-mm-dd format"],
     look_back_days: Annotated[int, "how many days to look back"],
 ) -> str:
+    # Validate ticker symbol to prevent path traversal
+    symbol = validate_ticker_symbol(symbol)
+
     # calculate past days
     date_obj = datetime.strptime(curr_date, "%Y-%m-%d")
     before = date_obj - relativedelta(days=look_back_days)
@@ -53,6 +86,9 @@ def get_YFin_data(
     start_date: Annotated[str, "Start date in yyyy-mm-dd format"],
     end_date: Annotated[str, "End date in yyyy-mm-dd format"],
 ) -> str:
+    # Validate ticker symbol to prevent path traversal
+    symbol = validate_ticker_symbol(symbol)
+
     # read in data
     data = pd.read_csv(
         os.path.join(
@@ -129,6 +165,8 @@ def get_finnhub_company_insider_sentiment(
     Returns:
         str: a report of the sentiment in the past 15 days starting at curr_date
     """
+    # Validate ticker symbol to prevent path traversal
+    ticker = validate_ticker_symbol(ticker)
 
     date_obj = datetime.strptime(curr_date, "%Y-%m-%d")
     before = date_obj - relativedelta(days=15)  # Default 15 days lookback
@@ -166,6 +204,8 @@ def get_finnhub_company_insider_transactions(
     Returns:
         str: a report of the company's insider transaction/trading informtaion in the past 15 days
     """
+    # Validate ticker symbol to prevent path traversal
+    ticker = validate_ticker_symbol(ticker)
 
     date_obj = datetime.strptime(curr_date, "%Y-%m-%d")
     before = date_obj - relativedelta(days=15)  # Default 15 days lookback
@@ -201,6 +241,8 @@ def get_data_in_range(ticker, start_date, end_date, data_type, data_dir, period=
         data_dir (str): Directory where the data is saved.
         period (str): Default to none, if there is a period specified, should be annual or quarterly.
     """
+    # Validate ticker symbol to prevent path traversal
+    ticker = validate_ticker_symbol(ticker)
 
     if period:
         data_path = os.path.join(