Use @{uid} instead of [0-9]* when it denotes the user id.

apparmor.d/groups/browsers/firefox

@@ -201,8 +201,8 @@ profile firefox @{exec_path} {
   @{user_share_dirs}/gvfs-metadata/home-*.log r,
 
   include <abstractions/dconf>
-  owner @{run}/user/[0-9]*/dconf/ rw,
-  owner @{run}/user/[0-9]*/dconf/user rw,
+  owner @{run}/user/@{uid}/dconf/ rw,
+  owner @{run}/user/@{uid}/dconf/user rw,
 
   profile open {
     include <abstractions/base>
@@ -219,7 +219,7 @@ profile firefox @{exec_path} {
 
     owner @{HOME}/ r,
 
-    owner @{run}/user/[0-9]*/ r,
+    owner @{run}/user/@{uid}/ r,
 
     # Allowed apps to open
     /{usr/,}bin/vlc              rPx,