plugins run in taint mode because the uid is changed, so the path must not
contain writable directories.

--- node/sbin/munin-node.orig	2020-03-24 12:31:00 UTC
+++ node/sbin/munin-node
@@ -53,6 +53,10 @@ sub main
         $ENV{$key} = $1;
     }
 
+    # plugins run in taint mode because the uid is changed, so the path
+    # must not contain writable directories.
+    $ENV{PATH}='/bin:/sbin:/usr/bin:/usr/sbin:%%PREFIX%%/bin:%%PREFIX%%/sbin';
+
     parse_args();
 
     my $config = Munin::Node::Config->instance();