[exim] exim-4.96RC0 - broken Mailman (2.x)

I must admit I have zero clue how to detaint this:

LOG: MAIN
** mailman@??? <mailman-bounces+moses=
XXXXXX.org@???> R=mailman_router T=mailman_transport:
Tainted arg 1 for mailman_transport transport command: 'bounces'

mailman_router:
  driver                     = accept
  require_files           = MAILMAN_HOME/lists/$local_part/config.pck
  domains                 = +mm_domains
  headers_remove    = ${if eq{SPAMHEADERTYPE}{0}{X-Spam-Score}}
  headers_remove    = ${if eq{SPAMHEADERTYPE}{0}{X-Spam-Report}}
  headers_remove    = ${if eq{SPAMHEADERTYPE}{0}{X-Spam-Score-Integer}}
  headers_remove    = ${if eq{SPAMHEADERTYPE}{0}{X-Spam-Flag}}
  transport                 = mailman_transport
  local_part_suffix = -bounces : -bounces+* : \
                      -confirm+* : -join : -leave : \
                      -owner : -request : -admin
  local_part_suffix_optional

mailman_transport:
  driver                 = pipe
  command           = MAILMAN_WRAP \
                      '${if def:local_part_suffix \
                      {${sg{$local_part_suffix}{-(\\w+)(\\+.*)?}{\$1}}} \
                      {post}}' \
                      $local_part
  current_directory = MAILMAN_HOME
  home_directory    = MAILMAN_HOME
  user                      = MAILMAN_USER
  group                    = MAILMAN_GROUP

LOG: MAIN
** mailman@??? <mailman-bounces+moses=
XXXXXX.org@???> R=mailman_router T=mailman_transport:
Tainted arg 1 for mailman_transport transport command: 'bounces'

--
Best regards,
Odhiambo WASHINGTON,
Nairobi,KE
+254 7 3200 0004/+254 7 2274 3223
"Oh, the cruft.", egrep -v '^$|^.*#' ¯\_(ツ)_/¯ :-)