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.