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According to this one, there could be over 4 million sites effected, which includes some mobile apps. https://github.com/pirate/sites-using-cloudflare
Also remember this does effect other furry related sites using cloudflare services, including furaffinity, weasyl and patreon, not just e6.
It does already help if you are doing your basic account security correctly, meaning 2fa on at least most important services, differend password on every single service, passwords that are hard to use brute force, changing password periodically on services you use commonly especially if they do not allow 2fa, etc. This way even if single login has bled from this mess, it means attacker can only access that one account of yours, if even that.
Good password managers (not the one build in browser) can also help to avoid falling into pitfalls like easy/same passwords and avoid keyloggers getting information, but in cases like this they bleed exactly the same as other passwords.