In Advantech Spectre RT Industrial Routers ERT351 5.1.3 and prior, the affected product does not neutralize special characters in the error response, allowing attackers to use a reflected XSS attack.
https://us-cert.cisa.gov/ics/advisories/icsa-21-054-03
https://ep.advantech-bb.cz/support/router-models/download/511/sa-2021-01-fw-5.1.3-and-older-en.pdf