There are accusations that Red Bull have bent (literally) the rules by using a rear wing that flexes at speed which has a similar influence on straight line speed as the DRS. FIA isn't pointing any fingers but they have contacted all teams saying it has become aware that some aerodynamic devices although rigid in a static test deflected at speed. The FIA is to carry out deflection tests and also use the cameras on the cars to monitor the wings.
https://www.bbc.co.uk/sport/formula1/57086036