new_contents: from trac.core import *
  from trac.config import ListOption
  from trac.perm import IPermissionPolicy, IPermissionRequestor, PermissionSystem
  from trac.ticket.model import Ticket
  
  
  class SecurityTicketsPolicy(Component):
      """
      Require the VULNERABILITY_VIEW permission to view any ticket with the words
      "security" or "vulnerability" in the summary or keywords fields.
      """
      implements(IPermissionPolicy, IPermissionRequestor)
  
      # IPermissionPolicy methods
      def check_permission(self, username, action, context):
          # Find available ticket context
          while context.parent:
              if context.realm == 'ticket':
                  break
              context = context.parent
  
          if context.realm == 'ticket' and context.id is not None:
              ticket = Ticket(self.env, context.id)
              fields = (ticket['keywords'] + ticket['summary']).lower()
              if 'security' in fields or 'vulnerability' in fields:
                  perms = PermissionSystem(self.env).get_user_permissions(username)
                  if 'VULNERABILITY_VIEW' not in perms:
                      return False
  
      # IPermissionRequestor methods
      def get_permission_actions(self):
          yield 'VULNERABILITY_VIEW'
  
subject: Add the `vulnerability_tickets.py` sample security plugin to deny access to tickets with "security" or "vulnerability" in the `keywords` or `summary` fields.