The variability of X-ray detections in the 3XMM catalogue is explored through their fractional variability and chi-squared tests. However, some sources may show very short duration outbursts, resulting in few X-ray counts and thus having insufficient counts over a long observation to be detected. Examples of such objects are distant and thus strongly redshifted faint short gamma-ray bursts that last less than two seconds, the electromagnetic counterparts of gravitational wave events. Alternatively these could be type-I X-ray bursts in distant galaxies, or possibly X-ray counterparts to fast radio bursts (FRBs). Building on existing software, I am developing an algorithm to automatically search XMM-Newton data for new sources that may have shown very short outbursts, but which are drowned out by the background noise summed over the whole observation. Searching for new objects in short time bins throughout the duration of the observation may be one way to identify these sources. Here I will present the variability tests and results of the most interesting variable sources discovered. This code could be used to conduct automatic searches across observations to search for gravitational wave event counterparts as well as other fast transients.