[exim] Taint mismatch, string_nextinlist: acl_check_conditio…

It doesn't seem like my config is functional from 4.93 any longer
Can sombody help me give direction what to change?

set acl_m0       = $local_part@$domain

warn     spam    = $acl_m0:true
      add_header  = X-Spam-Report: $spam_report

Thanks so much