Update pfsense_clickjacking.md

Author: ykoster

documentation/modules/exploit/unix/http/pfsense_clickjacking.md

@@ -4,7 +4,7 @@ This vulnerability affects any pfSense versions prior to 2.4.2-RELEASE.
 
 ## Vulnerable Setup
 
-The victim should be able to access the WebGUI & must be logged in as admin in order for this exploit to work. Possible the WebGUI's TLS certificate must be trusted in the browser.
+The victim should be able to access the WebGUI & must be logged in as admin in order for this exploit to work. Possibly the WebGUI's TLS certificate must be trusted in the browser.
 
 ## Verification Steps