stop ads in firefox tabs

See Sponsors on the home page and New Tab page how to disable promoted content.

If you want to disable the stories there's a preference: Customize items on your Firefox New Tab page

And seriously: Do NOT use similar-purposed blocker(s) along with uBlock Origin: this will cripple uBO's ability to defuse anti-blocker mechanisms and its ability to minimize likelihood of site breakage.

Are these so called Ads popping up on the bottom right corner of Firefox window?. If so then these are likely just Web Push Notifications from sites you have allowed to send you notifications. They can be useful information or even junk, spam, or fake virus/trojan alerts. You can revoke the sites from sending you notifications as explained in the kb article below.

https://support.mozilla.org/en-US/kb/push-notifications-firefox