When I checked with ENS 10.5.3 not supported to latest Firefox browser so here what would be workaround.
and also when i addons the extension then it is showing Legacy Extension, why is showing legacy extension
anyone can have the answer of above this.
first of all, it would be better to post ENS questions in the Enterprise Forum, there you would get faster response.
Managing WebContent with Browser Plugins is always a challenge. So you have to decide how to handle this, how your company handles this. This means, you need a clear defined strategy which Browsers are allowed and which not. You have to block automated upgrading ob browsers.
This all also makes no sense when you do not block any unwanted browser or unwanted application which connects to the internet.
One easy way is to move from an endpoint product only to a browser and endpoint software independent approach. One solution is MCP (McAfee Client Proxy). This small tool redirects any traffic on the endpoint from any application to a secure web gateway.
The next level, if it is possible in your company, implement a transparent proxy.
Finally, if you only want to do something on the endpoint, take care about Browser versions.