This release addresses several security problems.
CVE-2019-19911 is regarding FPX images. If an image reports that it has a large number of bands, a large amount of resources will be used when trying to process the image. This is fixed by limiting the number of bands to those usable by Pillow.
CVE-2020-5310: Overflow checks have been added when calculating the size of a memory block to be reallocated in the processing of a TIFF image.