Verify 'Full Name' field does not allow HTML in Signup form

'Full Name' field in the signup form is allowing HTML as an input
which makes spoofing easily.To avoid it, validation is added
that will ensure 'Full Name' field does not allow HTML.

LEARNER-3385

common/djangoapps/student/forms.py

@@ -128,6 +128,16 @@ def validate_username(username):
     validator(username)
 
 
+def validate_name(name):
+    """
+    Verifies a Full_Name is valid, raises a ValidationError otherwise.
+    Args:
+        name (unicode): The name to validate.
+    """
+    if accounts_settings.api.contains_html(name):
+        raise forms.ValidationError(_('Full Name cannot contain the following characters: < >'))
+
+
 class UsernameField(forms.CharField):
     """
     A CharField that validates usernames based on the `ENABLE_UNICODE_USERNAME` feature.
@@ -192,7 +202,8 @@ class AccountCreationForm(forms.Form):
         error_messages={
             "required": _NAME_TOO_SHORT_MSG,
             "min_length": _NAME_TOO_SHORT_MSG,
-        }
+        },
+        validators=[validate_name]
     )
 
     def __init__(