The cloud “save” button in the UI for this addon if not intentially designed to trick users into clicking it first rather than the real download button next to it has that affect anyway.
Screenshot below for reference, the cloud save button is far more prominent on the dialog that the local download button, this is likely to cause users to click the cloud upload button instead of the download button when trying to save an image locally.
I decided to use this feature to save a screenshot as it saves me having to crop a screenshot in GIMP or some other utility after taking it, after cropping some fairly personal details I then hit the clearly marked highlighted “Save” button to then discover that it doesn’t infact “Save” locally but instead uploads it directly to Mozilla new public image host.
This could easily have disastrous consequences for someone that was cropping sensetive information from their web browser such as payment details or anything else users would rather not share with the whole world on a publicly accessible image host.
Also I don’t know what kind of checks you enforce on users trying to delete an image, but it’s incredibly frustraiting being met with the error “Error deleting shot” when trying to delete something you accidentaly “saved” less than 30 seconds ago.
I’d suggest you remove the “Save” text from the button entirely or change it to “Share” instead, that way it would be far more clear what it’s intended purpose is and would not result in users mistakenly using it instead of the adjacent download button.