Random insertions are identified by strategically placing the guide RNAs (gRNAs) used in the CRISPR-KRISPR assay: one gRNA in one of the homology arms and the second binding to an overlapping region between the insert and the other arm. See article for more details.
The CRISPR-KRISPR method can also be useful for characterizing knock-in loci in other model organisms, including cell lines!