For some time now, Firefox browsers (38.0.5 and later) have shown Pocket's service in the top right corner. This extension is built into Firefox by default. Pocket lets you save webpages, videos, and articles from Firefox and read them offline. The stored content is available on all systems, regardless of whether it is a smartphone, computer or tablet. If you don't need this feature on your Firefox, you can disable Pocket.
Disable Pocket in Firefox
Here we introduce two methods on how to get rid of Pocket.

First Method
Right-click the Pocket icon and select Remove from Toolbar.

Restart your Firefox browser and Pocket will be gone.