As said before. It collects your data in the really sneaky way. It was banned from AMO for some time.
Really sad that it returned here (guess because of updated description that now mentions that our data is collected).

Once a great extension, now spyware. Use "Stylus" instead.

I uninstalled this app when they started collecting all your information without disclosure and selling it, then they are finding ways to reinstall this addon without your permission. Please remove this addon from Firefox, it's on the level of malware now.

Who removes every single older version of their addon from addons.mozilla.org? A douche bag, that's who.

It is Spyware, steals user data and all history of visited URLs. More info: https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/

Use safe Stylus add-on instead!

Don't use it: changed owners, can no longer be trusted. Switch to Stylus instead.

DO NOT INSTALL - version 3.1.5 is still SPYWARE that records personal information from all visited website.
Good alternative: https://addons.mozilla.org/en-US/firefox/addon/styl-us/

為何舊版本全部刪除？我想下載早期原作者開發的版本

SPYWARE, DO NOT INSTALL IT

Spyware

DO NOT INSTALL STYLISH. This addon is spyware that will steal your internet history.

https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/

DO NOT DOWNLOAD. THEY COLLECT ALL YOUR BROWSING HISTORY!
https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/
----------------------------------------------------------

(Hi, you can take full control over the data you share and can amend these details from the settings page. Please feel free to read the Stylish Privacy Policy for more information regarding this issue: https://userstyles.org/login/policy)

That's cute, full control? Geewiz! Does that control allow me to destroy all the data you have collected? You're a menace to society. However you convince yourself that your behavior is acceptable is beyond me.

True, the fault is mine for putting my trust into the old dev, but there's no shortage of leeches and sadly that's all you'll ever be in your miserable life. Keep telling yourself that people have "full control". Despicable.

I rather use my "full control" to wipe you off this platform and expose you for what you really are.

Spyware, stealing usage info and browser history

It has for more that a year broken GDPR; that is, it KNOWINGLY SELLS AND USES YOUR PRIVATE USAGE AND HISTORY, without even warning you.

If you want a add-on that doesn't try to sell your history, have a look at Stylus.
More information here https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/

Works, but 1 star because history stealing enabled by default. Good bye, Stylish.
https://robertheaton.com/2018/07/02/stylish-browser-extension-steals-your-internet-history/