I think that you are noticing the 'diffraction spikes'?- (simplistically!) the six main ones are caused by the hexagonal shape of the mirror segments of the JWST, and the two smaller spikes caused by the secondary mirror supports.
(See page 23 of the attached for the science!
).
They are prominent on the image due to the foreground stars being very bright compared to the background (when it's the background that's really of interest).
This effect will only occur for a limited set of images (say deep fields, or where the effect can actually help with the mirrors calibration).
JWST itself is an anastigmat telescope - so hopefully shouldn't have astigmatism!
The James Webb Space Telescope (sometimes called Webb or JWST) is a large infrared telescope with a 6.5-meter primary mirror. Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the history of our Universe, ranging from the...
webb.nasa.gov
I hope that makes sense?