Elasticsearch cut strings with forward slash

I have configured my squid proxy to send the logs to Elasticsearch 7.17.6, everything is working fine, except the USER mapping.

The string expect is DOMAIN/USER, the ELK recieves it correctly on original message but then on mapping I just see DOMIN, /USER is missed.

The field type is configured as keyword in mapping and index patterns.

Anyone can help me to solve this issue.

Thanks in advance

Best regards

Problem fixed

In grok i must use

(%{DATA:squid.proxy.user}|-)

instead of

(%{USER:{DATA}|-)