Citrix Web Application Firewall (WAF) announces periodic signature updates that you can download and apply on your appliance. When you detect a security attack, you will receive an email notification about the new signature update. You can download the signature and apply it on your appliance.
New signatures rules are generated for the vulnerabilities identified in the week 2019-12-19. You can download and configure these signature rules to protect your appliance from security vulnerable attacks.
For more details please refer: https://docs.citrix.com/en-us/citrix-adc/13/application-firewall/signature-alerts/document-history.html