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
# -*- coding: utf-8 -*-

"""

URL Check

URL查重处理

@dependencies:

1. mmh
2. bitarray

"""
import re
import math
import random

import mmh3
from bitarray import bitarray


urls = [
    'https://www.zhihu.com/question/26006703',
    'https://www.zhihu.com/roundtable/jiqixuexi',
    'https://www.zhihu.com/question/63883507/answer/227019715',
    'https://www.zhihu.com/question/63883507',
    'https://www.zhihu.com/people/breaknever/activities',
    'www.baidu.com',
    'https://www.zhiha.com/dqwfq3/',
    'https://www.zhihu.ca/wdqd21f'
]

"""
## URL Type:

* topic
* people
* roundtable
* question

"""


def get_url_type(url):
    """
    https://www.zhihu.com/xxxxx/1231234/xwf3qwrvq
    :param url:
    :return: xxxxxxx
    """
    x = url.split('?')[0]
    s = x.replace('//', 'a')
    s = s.split('/')
    if len(s) < 2:
        return None
    return s[1]


def get_url_id(url):

    """
    https://www.zhihu.com/question/xxxxxx/xwf3qwrvq
    :param url:
    :return: xxxxxxx
    """
    x = url.split('?')[0]
    s = x.replace('//', 'a')
    s = s.split('/')
    if len(s) < 3:
        return None
    return s[2]


def filter_urls(urls):
    """
    URL 过滤、标签
    过滤规则：知乎之外的网站、

    :param urls:
    :return: [(URL, URL_TYPE, URL_CONTENT)]
    """
    pattern = '(http|https)://www.zhihu.com/.*?'

    def match_(url):
        if re.match(pattern, url, re.S) is None:
            return False
        return True

    urls = filter(match_, urls)

    def get_type(url):

        s = url.replace('//', 'a')
        s = s.split('/')
        url_type = s[1]
        url_content = s[2]
        return url, url_type, url_content

    urls = map(get_type, urls)
    return urls


def check_urls(urls, bloom_filter):

    assert isinstance(bloom_filter, BloomFilter), "Use Bloom Filter"

    print(type(urls))

    def preprocess(x):
        """
        www.zhihu.com/quesiotn/dqwfqg[?w=cw&fqw=]
        :param x:
        :return:
        """
        x = x.split('?')[0]
        url_type = get_url_type(x)
        if url_type == 'question':
            url_id = get_url_id(x)
            if x is not None:
                return 'https://www.zhihu.com/question/%s' % url_id
        return x

    pattern = '(http|https)://www.zhihu.com/.*?'

    def match_(url):
        if re.match(pattern, url, re.S) is None:
            return False
        return True

    urls = filter(match_, urls)
    urls = map(preprocess, urls)


    result = []

    for url in urls:

        if len(url) == 0:
            continue
        if not bloom_filter.check(url):
            result.append(url)
            bloom_filter.add(url)

    return result


class BloomFilter(object):

    def __init__(self, item_count, prob):

        self.prob = prob
        self.size = self.get_size(item_count, prob)
        self.hash_count = self.get_hash_count(self.size, item_count)
        self.bit_array = bitarray(self.size)
        self.bit_array.setall(0)

    @classmethod
    def get_size(self, n, p):
        """

        :param n: numbers of elements in the filter
        :param p: False Positive Prob
        :return:
        """
        m = -(n*math.log(p))/(math.log(2)**2)
        return int(m)

    def check(self, item):
        for i in xrange(self.hash_count):

            digest = mmh3.hash(item, i) % self.size
            if not self.bit_array[digest]:
                return False
        return True

    def add(self, item):

        digests = []
        for i in xrange(self.hash_count):

            digest = mmh3.hash(item, i) % self.size
            digests.append(digest)

            self.bit_array[digest] = True

    @classmethod
    def get_hash_count(self, m, n):
        """
        k = (m/n)*lg(2)
        :param m: bit array size
        :param n: number of elements
        :return:
        """
        k = (m/n)*math.log(2)
        return int(k)


if __name__ == '__main__':

    urls = filter_urls(urls)
    for i in urls:
        print (i)
```

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