The Web-GUI on WAGO Series 750-88x (750-330, 750-352, 750-829, 750-831, 750-852, 750-880, 750-881, 750-882, 750-884, 750-885, 750-889) and Series 750-87x (750-830, 750-849, 750-871, 750-872, 750-873) devices has undocumented service access.
WAGO 750-88X and WAGO 750-89X Ethernet Controller devices, versions 01.09.18(13) and before, have XSS in the SNMP configuration via the webserv/cplcfg/snmp.ssi SNMP_DESC or SNMP_LOC_SNMP_CONT field.