One of the features of the iOS image editing tool is the highlighter. This allows users to highlight portions of text, which we imagine was the intended purpose, but we have also seen how some people have used the feature to try and censor sensitive information that they post onto social media.
This includes trying to censor names, dates, flight ticket numbers, and so on. It seems get the job done, but should you use it? Maybe not, because in a post on Reddit, u/M1ghty_boy has revealed that with a bit of image manipulation by cranking up the exposure, highlights, shadows, and contrast, you can actually reveal the information that was previously censored.
This is due to the default settings of the highlighter tool where its opacity is not set at 100%, meaning that it is somewhat see-through. Now, this isn’t really a bug or a security flaw since we imagine that this is not what Apple had intended, so we don’t think that it needs to be “fixed”. Instead, if you do need to censor information, try cranking up the opacity to 100% or use a solid color filled shape which will probably do a better job.
In the meantime, if you have any posts on social media that have been censored using the highlighter tool, then maybe you might want to take it down.