* Warning: HTTP/HTTPS mixed content blocking does not work in Fission yet. ({{bug|1584157}})
* Random crashes, including CreateFromIPC top crash X Windows stability issues when opening many Flash tabs on Linux. {{bug|16256031129492}}.
* Some extensions might not work fully. But please file bugs for any of these issues!
* Some DevTools issues debugging Fission tabscross-origin iframes.* Some video player issues on YouTube and Twitch.({{bug|1619370}}, {{bug|1620341}})
* Session restore does not restore page zoom level.
* Duo 2FA passcode input may not work, but Duo Push works correctly.
* Cross-origin iframes will appear empty when printed.
* Cross-origin iframes may occasionally appear in global history.