diff --git a/main.py b/main.py
index 544f2a1..94b1713 100644
--- a/main.py
+++ b/main.py
@@ -19,7 +19,9 @@
 import logging
 import time
 import re
+import ipaddress
 from typing import Dict, List, Optional, Any, Set, Sequence
+from urllib.parse import urlparse
 
 import httpx
 from dotenv import load_dotenv
@@ -99,10 +101,75 @@ def _api_client() -> httpx.Client:
 
 
 def validate_folder_url(url: str) -> bool:
-    """Validate that the folder URL is safe (HTTPS only)."""
+    """
+    Validates that the folder URL is safe for use by enforcing strict security boundaries.
+
+    Validation behavior:
+    1. Only HTTPS URLs are allowed.
+    2. Only URLs with hostnames matching the following domains (or their subdomains) are allowed:
+       - github.com
+       - githubusercontent.com
+    3. URLs with direct IP addresses (both IPv4 and IPv6) are blocked.
+    4. The following types of IP addresses are explicitly rejected:
+       - Private (e.g., 10.0.0.0/8, 192.168.0.0/16)
+       - Loopback (e.g., 127.0.0.1, ::1)
+       - Link-local (e.g., 169.254.0.0/16, fe80::/10)
+       - Reserved addresses
+    5. Subdomain matching is supported for allowed domains (e.g., raw.githubusercontent.com is allowed).
+
+    This helps prevent SSRF attacks by restricting access to trusted, public resources only.
+    """
+    # Check HTTPS protocol
     if not url.startswith("https://"):
-        log.warning(f"Skipping unsafe or invalid URL: {url}")
+        log.warning(f"Skipping unsafe or invalid URL (not HTTPS): {url}")
+        return False
+    
+    # Allowlist of trusted domains
+    ALLOWED_DOMAINS = {
+        "github.com",
+        "githubusercontent.com",
+    }
+    
+    try:
+        parsed = urlparse(url)
+        host = parsed.hostname
+        
+        if not host:
+            log.warning(f"Skipping invalid URL (no hostname): {url}")
+            return False
+        
+        # First, check if the hostname is an IP address
+    except Exception as e:
+        log.warning(f"Parsing error while validating URL {url}: {e}")
+        return False
+    
+    if not host:
+        log.warning(f"Skipping invalid URL (no hostname): {url}")
+        return False
+    
+    # First, check if the hostname is an IP address
+    # If it is, ensure it's not a private IP (reject all direct IP access)
+    try:
+        ip = ipaddress.ip_address(host)
+        if ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved:
+            log.warning(f"Skipping URL with private/internal IP address: {url}")
+            return False
+    except ValueError:
+        # Not an IP address, it's a domain name - continue with domain validation
+        pass
+    
+    # Check if host is in allowlist (including subdomains)
+    host_lower = host.lower()
+    is_allowed = False
+    for allowed_domain in ALLOWED_DOMAINS:
+        if host_lower == allowed_domain or host_lower.endswith(f".{allowed_domain}"):
+            is_allowed = True
+            break
+    
+    if not is_allowed:
+        log.warning(f"Skipping URL from untrusted domain: {url} (host: {host}) [rejected for security reasons]")
         return False
+    
     return True