This is the clipping indicator for highlights. To remove it, press J once or twice or thrice
Awesome! That took care of it! Thank you!! ;-D
Besides using the J key, the clipping indicators can be turned on and off by clicking the little triangles at the top left and top right of the histogram.
That took care of it!
Yes it may have cancelled the clipping indicator in LR,
BUT did you correct your exposure, highlights, whites, etc, so as to NOT have clipping?
Clipping indicates areas where you do not have any image detail- something you should avoid, either by better camera exposure technique or corrections in editing.