Comment by jpetrucc

posting a snippet for HAProxy in case its helpful to someone else (or if others have recommendations on how to better do this)

  http-request deny if { path -m sub ${ }
  http-request deny if { query -m sub ${ }
  http-request deny if { path -m sub $%7B }
  http-request deny if { query -m sub $%7B }
  http-request deny if { path -m sub %24%7B }
  http-request deny if { query -m sub %24%7B }