Streams in PDF files can be compressed, which may result in "deflate bombs" if not handled by the PDF processing application. Find attached three simple PDF compression bombs (10MB on disk to 10GB in memory). Note the compressed stream can be used multiple times in a single PDF document. The PDF files have been gzipped as a precaution mechanism, in order to prevent DoS when accidentally previewing them (gunzip them before the actual testing). Maybe resource limitations should be enforced by Okular / Poppler?
Created attachment 125332 [details] Trivial PDF deflate bomb (01)
Created attachment 125333 [details] Trivial PDF deflate bomb (02)
Created attachment 125334 [details] Trivial PDF deflate bomb (03)
Okular doesn't do any pdf parsing. Please report upstream at poppler.
I opened an issue for Poppler: https://gitlab.freedesktop.org/poppler/poppler/issues/878 If it's handled there, things should be fine.