Is there a threat from screenshots with blacked out info? That is can someone take out that aftermarket addition so to speak?

For instance

I take a screenshot (using MS snipper)




Then I 'blur/blackout' some info


Is the picture above vulnerable to someone looking through its hex values for that extra green layer and just removing it, thus reconstructing the original image (or any other way to 'take off' my attempt of redacting info)?



To make it more secure I always then open up the blurred out screen and then screen capture that.
 

Does the above screen of a screen add better security -there is no way to reconstruct missing data because nothing is "missing"?



I have always been paranoid but after finding out a colleague does the same thing, I'd thought I'd ask.



update So I compared pics one and two (from above) and looked at the hex values, the metadata had not changed at all and the only change was within the image data itself (results below). The results are specific to this particular editor and process. The possibility (likelihood) does exist for data to be recovered if using other tools.


Usually the PNG format does not support multiple layers. So when you draw over something, whatever was there before is lost.

However, the PNG format supports storage of an unlimited amount of metadata which is usually not displayed by image viewers. This feature is often used by image editors to add additional metadata to the image. One possible use-case is to store the undo-history of the image. This could mean that the previous version can be restored. To prevent this, make sure to set the exporting settings of your editor in a "export for web" mode which is supposed to strip all unnecessary data from the file. How to do this (and if it is even necessary) depends on the image editor.

Another possible faux-pas is to use an image blurring method which isn't 100% effective. You could, for example, accidentally set the opacity of your brush to almost but not completely 100%, which would mean that the section isn't recognizable by the human eye but might be made readable again by enhancing the contrast of the section. Another mistake is to use a filter which is reversible. I remember a case of a child-pornographer who got caught because he blurred out his own face with the "twirl" filter in Photoshop not realizing that when the same filter is applied in reverse, the image is restored to almost the original.
