Hmmm. Hasn't exactly worked for me. I replaced FORUM/assets/plupload/plupload.full.min.js with the new v.2.3.6.
But, the attachments don't render in post with the correct orientation. However, if you open the direct URL of the uploaded image in a new tab it is correctly oriented. The means the EXIF data is just being retained and properly interpreted by the browser, but not phpBB.
Now, looking into it further, since replacing with plupload 2.3.6, all attachments retain their complete EXIF data, including GPS coordinates. This was not the case previously and EXIF was stripped (which is a good thing!)
The preserve headers false option can be used to strip EXIF but i didn't actually have this flag before. I had an unmodified plupload.php.
I have tried changing max image dimensions to zero, and same result (but obviously image size then isn't reduced). Then, to ensure i hadn't changed something manually into the past, i went and replaced phpbb/plupload/plupload.php with the version that shipped with my forum download package (v.3.2.2). No change.
I wonder where I'm going wrong?
perhaps because I'm still on 3.2.2?