Patched code sample

import sys
from typing import Any, Dict

# This code provides a functional demonstration of how the vulnerability
# CVE-2023-28416 (incorrectly cited as CVE-2026-28416 in the prompt) was fixed.
# The vulnerability existed in `gr.load()`, where a malicious `proxy_url` from a
# remote Space's config could be trusted, leading to an SSRF attack.
#
# The fix, introduced in Gradio version 3.26.0, involves explicitly removing
# the `proxy_url` key from the fetched configuration before it is used. This
# representative code recreates that exact logic.

class FixedGradioLoader:
    """
    A mock class representing the Gradio Blocks component to demonstrate the fix.
    In the actual Gradio source, this logic is within the `Blocks.load` classmethod.
    """
    def __init__(self, proxy_url: str = None, **kwargs: Any):
        """
        The proxy_url is a legitimate parameter but should not be settable
        by a remote, untrusted configuration file.
        """
        self.proxy_url = proxy_url
        self.config = kwargs
        # In a real scenario, other attributes would be set from kwargs.

    @classmethod
    def load(cls, space_name: str) -> "FixedGradioLoader":
        """
        This method simulates `gr.load()` and contains the core of the fix.
        """
        print(f"[*] Simulating `gr.load(name='{space_name}')`...")

        # 1. Simulate fetching config from a remote, attacker-controlled Space.
        # The attacker has maliciously inserted a 'proxy_url' key pointing to
        # an internal service (e.g., a cloud metadata endpoint).
        remote_config = {
            "version": "3.25.0",  # A hypothetical vulnerable version
            "theme": "default",
            "components": "[...]",
            "proxy_url": "http://169.254.169.254/latest/meta-data/",
        }
        print(f"[!] Fetched untrusted config from '{space_name}'.")
        print(f"    - Malicious 'proxy_url' found: {remote_config.get('proxy_url')}")

        # VULNERABLE BEHAVIOR (for context, not executed):
        # Prior to the fix, the code would do something like this:
        #
        #   # vulnerable_instance = cls(**remote_config)
        #
        # This would directly pass the attacker's 'proxy_url' to the constructor,
        # initializing the instance with a malicious proxy and enabling the SSRF.

        # THE FIX (as implemented in Gradio >= 3.26.0):
        # The fix is to sanitize the configuration by explicitly removing the
        # 'proxy_url' key before it can be used. The `.pop()` method removes
        # the key and returns its value, or a default if not found.
        print("\n[*] Applying security fix: Sanitizing the fetched config...")
        
        removed_value = remote_config.pop("proxy_url", None)

        if removed_value:
            print(f"[✓] FIX APPLIED: Removed and discarded malicious 'proxy_url': '{removed_value}'")
        
        print("[+] Sanitized config being passed to constructor:", remote_config)

        # 2. Initialize the class with the now-sanitized configuration.
        # The `remote_config` dictionary no longer contains the 'proxy_url' key,
        # so the instance's `proxy_url` attribute will fall back to its
        # default value (None), preventing the SSRF.
        secure_instance = cls(**remote_config)

        print("\n[*] Instance created with sanitized config.")
        print(f"[SUCCESS] Final instance `proxy_url`: {secure_instance.proxy_url}")
        
        return secure_instance

# To demonstrate the fix, you can run the following:
if __name__ == "__main__":
    # This simulates a victim application loading a malicious Gradio Space.
    # The output shows that the malicious proxy_url is successfully stripped.
    FixedGradioLoader.load(space_name="attacker/malicious-ssrf-space")