Yes, students can take one bathroom break of up to 5 minutes during the exam. Before doing so, students should advise the invigilator using the chat function that they are leaving their desk to use the bathroom. Students only need to inform their invigilator before taking this break, permission does not need to be sought, so there is no need to wait for the invigilator response before leaving your desk.
The exam timer will continue to run during a bathroom break and on returning to your desk you should use the chat function to let the invigilator you have returned and then you can immediately continue with your exam, however, you may be asked by the invigilator to verify your ID again.
It is important that you do not exceed the 5 minute time limit permitted as this may result in your exam being terminated.