Patched code sample

import ast

def import_attachment(attachment_content):
    """Secure function that fixes the vulnerability."""
    content = escape_user_input(attachment_content)
    if check_code(content) and not contains_blacklisted_keywords(content):
        execute_code(content)
    else:
        print("Rejected unsafe code.")

def escape_user_input(user_input):
    """Secure function that fixes the vulnerability."""
    escape_mapping = {
        '<': '<',
        '>': '>',
        '{': '{',
        '}': '}',
        '$': '$',
        '#': '#',
        '%': '%',
        '&': '&',
    }
    for char, escaped in escape_mapping.items():
        user_input = user_input.replace(char, escaped)
    return user_input

def contains_blacklisted_keywords(code):
    """Secure function that fixes the vulnerability."""
    blacklist = ['import', 'exec', 'eval', 'open', 'os', 'subprocess', '__', 'globals', 'locals', 'input', 'compile', 'system']
    return any(word in code for word in blacklist)

def check_code(code):
    """Secure function that fixes the vulnerability."""
    try:
        tree = ast.parse(code, mode='exec')
        for node in ast.walk(tree):
            if isinstance(node, ast.Name) and node.id not in {"print"}:
                return False
            if not isinstance(node, (
                ast.Module, ast.Expr, ast.Call, ast.Name, ast.Load,
                ast.Constant, ast.BinOp, ast.Add
            )):
                return False
        return True
    except Exception:
        return False

def execute_code(code):
    """Secure function that fixes the vulnerability."""
    safe_globals = {"__builtins__": {"print": print}}
    exec(code, safe_globals)

attachment_content = "print('This is safe')"
import_attachment(attachment_content)