The Intershop Commerce Management (ICM) 188.8.131.52 release contains a Tomcat 9 update that affects all projects migrating to this version. In particular, it affects projects still using Solr 4, which is supported by Intershop only until the end of the year (see Announcement - End of Maintenance of Solr 4). Currently, Solr 4 in ICM is running on its own Tomcat 7. However, this "inner Tomcat" is removed with the Tomcat 9 update in ICM 7.10.31. In order to have a functioning Solr, project adaptions are necessary and a compatible ICM version must be used for the migration.