If a vulnerability has been found:

1. Go to the issues tab: https://github.com/LibreSprite/LibreSprite/issues
2. Write a full description of the problem
3. Add some screenshots and write your operating system version and device specifications

If there wasn't a response from the developers for a long period of time, you can go to the following links: https://discord.com/invite/95gbyU5 https://www.reddit.com/r/LibreSprite/