Disable sending fonts
In https://blog.torproject.org/comment/reply/1151/162098, Anonymous pointed out,
Then, the second question: Tools → Preferences → Content → "Send these fonts and colors as part of my messages when possible". ← What is this? Is it safe to allow? Why should I send any info about my fonts and colors to somebody? The interface should be standard for everybody.
That should be disabled and removed.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information