diff --git a/content/posts/adventofctf/challenge_21.md b/content/posts/adventofctf/challenge_21.md
index 6119cf2..bde20f5 100644
--- a/content/posts/adventofctf/challenge_21.md
+++ b/content/posts/adventofctf/challenge_21.md
@@ -11,8 +11,7 @@ tags = [
     "hacking",
     "writeup",
     "web",
-    "python",
-    "serialization",
+    "php",
 ]
 categories = [
     "ctf",