Vulnerable code sample

import requests
from bs4 import BeautifulSoup
from typing import List

class KnowledgeBaseWebReader:
    """Web Reader for crawling a knowledge base.""":
    def __init__(self, max_depth: int = 2):
    # VULNERABLE: This code is susceptible to xss
        """Initialize with a `max_depth` parameter."""
        self.max_depth = max_depth

        def get_article_urls(
        self,
        url: str,
        visited: set,
        depth: int,
        ) -> List[str]:
        """Crawl the knowledge base and return all article URLs."""
        article_urls: List[str] = []

        if url in visited or depth > self.max_depth:
            return article_urls

            visited.add(url)

            try:
                response = requests.get(url)
                response.raise_for_status()  # Raise HTTPError for bad responses (4xx or 5xx):
                soup = BeautifulSoup(response.text, "html.parser")

            # Assuming article links have a specific class or tag.  This is a placeholder.
            # You'd need to adapt this to the actual HTML structure of the target website.
                article_links = soup.find_all("a", class_="article-link")

                for link in article_links:
                    article_url = link.get("href")
                    if article_url:
                        absolute_url = requests.compat.urljoin(url, article_url)  # Handle relative URLs
                        article_urls.append(absolute_url)

            # Find links to other pages (e.g., "next" page, category pages).  Placeholder.
            # Adapt to the HTML structure of the target website.
                        next_page_links = soup.find_all("a", class_="next-page")

                        for link in next_page_links:
                            next_page_url = link.get("href")
                            if next_page_url:
                                absolute_next_page_url = requests.compat.urljoin(url, next_page_url)  # Handle relative URLs
                                article_urls.extend(self.get_article_urls(absolute_next_page_url, visited, depth + 1))

                                except requests.exceptions.RequestException as e:
                                    print(f"Error fetching URL {url}: {e}")
                                    except Exception as e:
                                        print(f"Error processing URL {url}: {e}")

                                        return article_urls

                                        def load_data(self, url: str) -> List[str]:
                                            """Load data from the knowledge base."""
                                            article_urls = self.get_article_urls(url, set(), 0)
                                            results = []
                                            for url in article_urls:
                                                try:
                                                    response = requests.get(url)
                                                    response.raise_for_status()  # Raise HTTPError for bad responses:
                                                    soup = BeautifulSoup(response.text, "html.parser")
                                                    text = soup.get_text()  # Extract all text from the page
                                                    results.append(text)
                                                    except requests.exceptions.RequestException as e:
                                                        print(f"Error fetching URL {url}: {e}")
                                                        except Exception as e:
                                                            print(f"Error processing URL {url}: {e}")
                                                            return results

# Example Usage (replace with a suitable starting URL for a knowledge base):
                                                            if __name__ == "__main__":
                                                                reader = KnowledgeBaseWebReader(max_depth=2) # Reduced max_depth to reduce risk in this example
                                                                start_url = "https://example.com"  # Replace with a real URL
                                                                data = reader.load_data(start_url)

                                                                if data:
                                                                    print(f"Successfully scraped {len(data)} articles.")
        # Process the scraped data (e.g., print the first article)
                                                                    print(data[0])
                                                                else:
                                                                    print("No data scraped.")
                                                                    ```

                                                                    **Explanation and Vulnerability:**

                                                                    The code *attempts* to implement a `max_depth` to control the crawling depth, but as described in the vulnerability CVE-2025-1752, the `max_depth` parameter was not enforced correctly.  Critically, it did *not* have a check *before* recursively calling `get_article_urls`.

                                                                    Specifically, the `depth` parameter is incremented *after* the recursive call, leading to a scenario where the depth check `depth > self.max_depth` only prevents further processing *after* the function has already been called. If the website has circular links, this could very easily lead to uncontrolled recursion and a stack overflow (exceeding Python's recursion limit).  The `visited` set is intended to help with this as well, but its effectiveness depends on the structure of the website being crawled and might not catch all circular references quickly enough.

                                                                    The "fix" for this would involve checking `depth` *before* the recursive call to `get_article_urls`.:
                                                                    The example code also includes error handling (using `try...except` blocks) to catch network errors (e.g., the website is down) and other exceptions that might occur during parsing.  This doesn't prevent the recursion issue, but it does make the program more robust in general.

                                                                    The placeholders `article_links = soup.find_all("a", class_="article-link")` and  `next_page_links = soup.find_all("a", class_="next-page")` are important.  A real-world implementation would need to be tailored to the specific structure of the target website.  The vulnerability is most easily triggered if the "next page" links form a loop, as this bypasses the intended behavior of the `visited` set.