The CVE of the IPS signature Mozilla.Firefox.PluginArray.NsMimeType.Code.Execution is CVE-2010-0177. This matches the CVE filter in the IPS sensor, so traffic is blocked and logged:
date=2022-07-24 time=15:44:56 logid="0419016384" type="utm" subtype="ips" eventtype="signature" level="alert" vd="vd1" eventtime=1594593896666145871 tz="-0700" severity="critical" srcip=10.1.100.22 srccountry="Reserved" dstip=172.16.200.55 srcintf="port2" srcintfrole="undefined" dstintf="port1" dstintfrole="undefined" sessionid=1638 action="dropped" proto=6 service="HTTPS" policyid=1 attack="Mozilla.Firefox.PluginArray.NsMimeType.Code.Execution" srcport=58298 dstport=443 hostname="172.16.200.55" url="/Mozilla" direction="incoming" attackid=20853 profile="sensor-1" ref="http://www.fortinet.com/ids/VID20853" incidentserialno=124780667 msg="web_client: Mozilla.Firefox.PluginArray.NsMimeType.Code.Execution," crscore=50 craction=4096 crlevel="critical"