diff --git a/backend/open_webui/routers/retrieval.py b/backend/open_webui/routers/retrieval.py
index dfd503f035..201e6a63fb 100644
--- a/backend/open_webui/routers/retrieval.py
+++ b/backend/open_webui/routers/retrieval.py
@@ -1567,6 +1567,8 @@ async def process_file(
 
             if collection_name is None:
                 collection_name = f'file-{file.id}'
+            else:
+                await _validate_collection_access([collection_name], user, access_type='write')
 
             if form_data.content:
                 # Update the content in the file
@@ -2617,6 +2619,9 @@ async def process_files_batch(
 
     collection_name = form_data.collection_name
 
+    if collection_name:
+        await _validate_collection_access([collection_name], user, access_type='write')
+
     file_results: List[BatchProcessFilesResult] = []
     file_errors: List[BatchProcessFilesResult] = []
     file_updates: List[FileUpdateForm] = []
diff --git a/backend/open_webui/utils/files.py b/backend/open_webui/utils/files.py
index 8149987fe4..6b821d58b6 100644
--- a/backend/open_webui/utils/files.py
+++ b/backend/open_webui/utils/files.py
@@ -26,7 +26,11 @@ import base64
 import io
 import re
 
-from open_webui.env import AIOHTTP_CLIENT_SESSION_SSL, ENABLE_IMAGE_CONTENT_TYPE_EXTENSION_FALLBACK
+from open_webui.env import (
+    AIOHTTP_CLIENT_ALLOW_REDIRECTS,
+    AIOHTTP_CLIENT_SESSION_SSL,
+    ENABLE_IMAGE_CONTENT_TYPE_EXTENSION_FALLBACK,
+)
 from open_webui.utils.session_pool import get_session
 
 BASE64_IMAGE_URL_PREFIX = re.compile(r'data:image/\w+;base64,', re.IGNORECASE)
@@ -53,11 +57,17 @@ _IMAGE_MIME_FALLBACK = {
 async def get_image_base64_from_url(url: str) -> Optional[str]:
     try:
         if url.startswith('http'):
-            # Validate URL to prevent SSRF attacks against local/private networks
+            # Validate URL to prevent SSRF attacks against local/private networks.
+            # allow_redirects=False prevents redirect-based SSRF: validate_url() is
+            # called only on the originally-submitted URL; following 3xx redirects
+            # without re-validation would let an attacker reach private IPs via a
+            # public host that redirects internally (e.g. cloud-metadata exfil).
             validate_url(url)
             # Download the image from the URL
             session = await get_session()
-            async with session.get(url, ssl=AIOHTTP_CLIENT_SESSION_SSL) as response:
+            async with session.get(
+                url, ssl=AIOHTTP_CLIENT_SESSION_SSL, allow_redirects=AIOHTTP_CLIENT_ALLOW_REDIRECTS
+            ) as response:
                 response.raise_for_status()
                 image_data = await response.read()
                 encoded_string = base64.b64encode(image_data).decode('utf-8')