diff --git a/src/routes/admin.py b/src/routes/admin.py
index ab46f11..8f847b7 100644
--- a/src/routes/admin.py
+++ b/src/routes/admin.py
@@ -1,3 +1,4 @@
+import logging
 import os
 import secrets
 from datetime import datetime, timezone
@@ -343,7 +344,6 @@ def song_details(track_id):
             "error_type": e["error_type"],
             "source": e["source"],
             "error_message": e["error_message"],
-            "stack_trace": e["stack_trace"],
             "created_at": e["created_at"],
         } for e in errors],
         "usage": {
@@ -379,8 +379,9 @@ def fetch_reference_lyrics(track_id):
     try:
         from src.services.reference_lyrics import fetch_lyrics
         lines = fetch_lyrics(title, artist, track_id=track_id)
-    except Exception as e:
-        return jsonify({"error": f"Lyrics fetch failed: {e}"}), 500
+    except Exception:
+        logging.getLogger(__name__).exception("Lyrics fetch failed for track %s", track_id)
+        return jsonify({"error": "Lyrics fetch failed"}), 500
 
     if not lines:
         return jsonify({"error": "No lyrics found"}), 404
@@ -431,8 +432,9 @@ def fetch_reference_lyrics_ai(track_id):
 
     try:
         lines = _fetch_openrouter(raw_text=raw_text, vocals_path=vp, track_id=track_id)
-    except Exception as e:
-        return jsonify({"error": f"AI lyrics fetch failed: {e}"}), 500
+    except Exception:
+        logging.getLogger(__name__).exception("AI lyrics fetch failed for track %s", track_id)
+        return jsonify({"error": "AI lyrics fetch failed"}), 500
 
     if not lines:
         return jsonify({"error": "AI returned no lyrics"}), 404
@@ -783,8 +785,10 @@ def _run_compress():
                     try:
                         compress_audio_file(path)
                         compressed += 1
-                    except Exception as e:
-                        print(f"Failed to compress {file_key} for track {tid}: {e}")
+                    except Exception:
+                        logging.getLogger(__name__).warning(
+                            "Failed to compress %s for track %s", file_key, tid, exc_info=True
+                        )
                         failed += 1
 
             log_event(
diff --git a/src/services/deezer.py b/src/services/deezer.py
index e7c3f9d..b8cc06a 100644
--- a/src/services/deezer.py
+++ b/src/services/deezer.py
@@ -1,9 +1,9 @@
 import sys
 import re
 import json
+import hashlib
 from typing import Optional, Sequence
 
-from Crypto.Hash import MD5
 from Crypto.Cipher import AES, Blowfish
 import struct
 import urllib.parse
@@ -141,8 +141,8 @@ def md5hex(data):
     """return hex string of md5 of the given string"""
     # type(data): bytes
     # returns: bytes
-    h = MD5.new()
-    h.update(data)
+    # MD5 is required by the Deezer download protocol — not used for security.
+    h = hashlib.md5(data, usedforsecurity=False)
     return b2a_hex(h.digest())
 
 
diff --git a/src/services/reference_lyrics.py b/src/services/reference_lyrics.py
index 0ad0028..2573385 100644
--- a/src/services/reference_lyrics.py
+++ b/src/services/reference_lyrics.py
@@ -1,9 +1,23 @@
 import base64
 import os
+from pathlib import Path
 
 import requests
 
 
+def _validate_file_path(file_path):
+    """Validate that *file_path* is within the songs directory."""
+    if not file_path:
+        return None
+    from src.utils.file_handling import _SONGS_PATH_RESOLVED
+    try:
+        resolved = Path(file_path).resolve()
+        resolved.relative_to(_SONGS_PATH_RESOLVED)
+        return str(resolved)
+    except (ValueError, TypeError):
+        return None
+
+
 def _fetch_lrclib(title, artist, track_id=None):
     """Fetch lyrics from lrclib.net (free, no API key, no Cloudflare)."""
     from src.utils.error_logging import log_event
@@ -86,7 +100,10 @@ def _fetch_openrouter(raw_text=None, vocals_path=None, track_id=None):
     # Try hybrid (audio + text) first, then fall back to text-only
     attempts = []
     if vocals_path and os.path.exists(vocals_path):
-        attempts.append("hybrid")
+        safe_vocals = _validate_file_path(vocals_path)
+        if safe_vocals:
+            vocals_path = safe_vocals
+            attempts.append("hybrid")
     attempts.append("text_only")
 
     for attempt in attempts:
diff --git a/src/utils/file_handling.py b/src/utils/file_handling.py
index b4c9813..0c493be 100644
--- a/src/utils/file_handling.py
+++ b/src/utils/file_handling.py
@@ -3,9 +3,24 @@
 import shutil
 import subprocess
 import tempfile
+from pathlib import Path
 from src.utils.constants import SONGS_DIR, TRACK_FILES
 
 SONGS_PATH = os.path.join(os.path.dirname(os.path.dirname(__file__)), SONGS_DIR)
+_SONGS_PATH_RESOLVED = Path(SONGS_PATH).resolve()
+
+
+def _validate_song_path(path):
+    """Resolve *path* and verify it stays within the songs directory.
+
+    Raises ValueError if the resolved path escapes SONGS_PATH.
+    """
+    resolved = Path(path).resolve()
+    try:
+        resolved.relative_to(_SONGS_PATH_RESOLVED)
+    except ValueError:
+        raise ValueError("Path traversal detected")
+    return str(resolved)
 
 
 def normalize_track_id(track_id):
@@ -27,8 +42,9 @@ def is_valid_track_id(track_id):
 def get_song_dir(track_id):
     track_id = normalize_track_id(track_id)
     path = os.path.join(SONGS_PATH, track_id)
-    os.makedirs(path, exist_ok=True)
-    return path
+    resolved = _validate_song_path(path)
+    os.makedirs(resolved, exist_ok=True)
+    return resolved
 
 
 def load_metadata(track_id):
@@ -114,8 +130,9 @@ def get_track_file_sizes(track_id):
 def delete_track(track_id):
     track_id = normalize_track_id(track_id)
     song_dir = os.path.join(SONGS_PATH, track_id)
-    if os.path.exists(song_dir):
-        shutil.rmtree(song_dir)
+    resolved = _validate_song_path(song_dir)
+    if os.path.exists(resolved):
+        shutil.rmtree(resolved)
         return True
     return False