I see here https://docs.lucee.org/reference/tags/cookie.html, Lucee list "samesite" attribute to use in cfcookie tag. I try to use that like

<cfcookie name="my_cookiesname" value="#mycookie_value#" expires="90" httponly="yes" secure="#application.x#" samesite="strict" />

But my Lucee said I don't know about samesite. Here is error screen shot. My Lucee version is Lucee 5.3.6.61 Can anybody help me why my Lucee is unable to idedidentify the samesite attribute?

i'd say try the same thing but in cfscript syntax vs cfml, see if there's a disconnect between tag/script implementation

if you are using an older version of Lucee, you first step is to check that latest version.... https://luceeserver.atlassian.net/issues/?jql=text%20~%20%22samesite%22 samesite was introduced in 5.3.7