system: You are an expert security code reviewer. You will be shown a source code file along with a catalog of candidate CWE (Common Weakness Enumeration) categories with their official MITRE names. Your task is to list every distinct CWE from that catalog that is actually present in the code. The catalog is comprehensive for this dataset -- the answer is a (possibly small) subset of it.

OUTPUT FORMAT: Respond with a comma-separated list of CWE IDs in the form `CWE-N`, sorted in ascending numeric order, wrapped in a single \boxed{...}. Examples: `\boxed{CWE-79}` for one, `\boxed{CWE-22,CWE-79,CWE-327}` for three. Output the boxed answer ONLY -- no explanation, no other text.

user: ```python
# validator for UrlSource

from typing import List, Callable, Dict, Union, Tuple
from loguru import logger
import pandas as pd
import re

from sources.url_source import UrlSource
from shared import udatetime

class UrlSourceValidator():

    def __init__(self):
        self._locations = {}
        self._urls = {}
        self._msg = []

        self.is_valid = False
        self.status_message = ""
        self.num_rows_with_errors = 0
        self.error_messages = []

    def _validate_location(self, location: str):    
        if location == None or location.strip() == "":
            self._msg.append(f"empty location")
        elif not re.match("[._A-Za-z0-9]+", location):
            self._msg.append(f"invalid location")
        elif location.endswith("_data"):            
            self._msg.append(f"location can't end with '_data'")
        else:
            parts = location.split(".")
            if len(parts[0]) != 2:
                self._msg.append(f"expected state abbreviation at start")

    def _validate_source(self, source: str):
        if not re.match("[_A-Za-z0-9]+", source):
            self._msg.append(f"invalid source")

    def _validate_url(self, kind: str, xurl: str):
        if xurl == None or xurl == "": return
        if not re.match("https?://.+", xurl):
            self._msg.append(f"invalid url {kind}: {xurl}")
        if xurl.startswith("https://google.com") or xurl.startswith("https://www.google.com"):
            self._msg.append("google is not allowed as an endpoint")

    def _validate_rows(self, name: str, df: pd.DataFrame) -> bool:

        self._locations = {}

        n = df.shape[0]
        for idx, r in df.iterrows():

            location = r["location"]
            source = r["source_name"]
            main_url = r["main_page"]
            data_url = r["data_page"]
            error_msg = r["error_msg"]

            self._msg.clear()

            # duplicate check
            prev_info = self._locations.get(location)
            if prev_info != None:
                psource, pidx, pmain_url, pdata_url = prev_info
                if main_url == pmain_url and data_url == pdata_url:
                    logger.info(f"  duplicate with {psource}:{pidx}") 
                else:
                    self._msg.append(f"conflict with {psource}:{pidx}")

            info = (source, idx, main_url, data_url)
            self._locations[location] = info

            if error_msg != None and error_msg != "":
                self._msg.append(f"[parser] msg={error_msg}")
            else:
                self._validate_location(location)
                self._validate_source(source)
                self._validate_url("main_page", main_url)
                self._validate_url("data_page", data_url)

            if len(self._msg) > 0:
                self.num_rows_with_errors += 1                
            for m in self._msg:
                self.error_messages.append(f"  {source} {idx} of {n}: {location} - {m}")

        return self.num_rows_with_errors == 0

    def validate(self, source: UrlSource) -> bool:

        self.is_valid = True
        self.status_message = f"Url source {source.name} is valid"

        if source.error_msg != None: 
            self.is_valid = False
            self.status_message = source.error_msg
            return False

        error_msg = self._validate(source)         
        if error_msg != None: 
            logger.error(f"validate returned: {error_msg}")
            source.status = "failed"
            source.error_msg = error_msg
            source.error_at = udatetime.now_as_utc()
            self.is_valid = False            
            self.status_message = f"Url Source {source.name} is not valid"            
            return False

        source.status = "valid"
        source.error_msg = None
        source.error_at = None
        return True

    def _validate(self, source: UrlSource) -> str:

        if source.df is None: 
            return "DataFrame is missing"
        if source.df.shape[0] == 0: 
            return "DataFrame is empty"

        if not "location" in source.df.columns: return "Missing location column"
        if not "main_page" in source.df.columns: return "Missing main_page column"
        if not "data_page" in source.df.columns: return "Missing data_page column"    
        if not "error_msg" in source.df.columns: return "Missing error_msg column"

        if self._validate_rows(source.name, source.df): return None
        return f"{self.num_rows_with_errors} rows are invalid"

    def display_status(self):

        if self.is_valid:
            if self.status_message != None:
                logger.info(self.status_message)
            return

        logger.error(self.status_message)
        for err_msg in self.error_messages:
            logger.error("  " + err_msg)


```

Candidate CWE catalog (every CWE that appears anywhere in this dataset):
  - CWE-20: Improper Input Validation
  - CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
  - CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
  - CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
  - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
  - CWE-89: Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')
  - CWE-94: Improper Control of Generation of Code ('Code Injection')
  - CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
  - CWE-116: Improper Encoding or Escaping of Output
  - CWE-117: Improper Output Neutralization for Logs
  - CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
  - CWE-209: Generation of Error Message Containing Sensitive Information
  - CWE-215: Insertion of Sensitive Information Into Debugging Code
  - CWE-295: Improper Certificate Validation
  - CWE-312: Cleartext Storage of Sensitive Information
  - CWE-326: Inadequate Encryption Strength
  - CWE-327: Use of a Broken or Risky Cryptographic Algorithm
  - CWE-377: Insecure Temporary File
  - CWE-502: Deserialization of Untrusted Data
  - CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
  - CWE-611: Improper Restriction of XML External Entity Reference
  - CWE-614: Sensitive Cookie in HTTPS Session Without 'Secure' Attribute
  - CWE-643: Improper Neutralization of Data within XPath Expressions ('XPath Injection')
  - CWE-730: OWASP Top Ten 2004 Category A9 - Denial of Service
  - CWE-732: Incorrect Permission Assignment for Critical Resource
  - CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
  - CWE-918: Server-Side Request Forgery (SSRF)
  - CWE-943: Improper Neutralization of Special Elements in Data Query Logic
  - CWE-1004: Sensitive Cookie Without 'HttpOnly' Flag
  - CWE-1333: Inefficient Regular Expression Complexity

List every distinct CWE from the catalog above that is actually present in this code.
Answer: CWE-20