Audible Backup is a Firefox add-on by Patrick Meyer. This add-on has 19 daily active users and a poor user rating of 2.00. The latest version, 9, was updated 3 years ago.
This plugin synchronizes your audible library with a backup server. It does not remove the DRM from your audiobooks. It simply downloads the AAX files via the normal download link in the audible web library.
After installing the plugin you have to first configure your backup URL via the plugins UI. To set the URL click the plugins icon in your address bar.
Currently this plugin is hardcoded to amazon.de
Security hole, and not really working. First, it wants permission to access all your data at all websites, when it does not need to do this. It only needs *.audible.[tld], and *.amazon.[tld], and optionally some site you control for uploads. I'll give it two stars for being functional as an addon at all; it appears in the menu, has an icon, has an interface, etc.
However, it doesn't seem to do anything if you tell it to save locally, with a file:///... URL (which is probably what 99.99% of people would want to do, since they are not administrators of some remote https://... website with WebDAV uploading). And this remote upload feature will only accept a URL as input, not separate user ID and password fields, so it appears that you'll have to URL-encode any necessary ID and password in the upload URL, which is yet another security hole.
And it appears to be hardcoded to use the amazon.de authentication interface, so if you are not in Germany (or using a VPN that spoofs you being in Germany), you can't use this at all. Which makes very little sense, since the interface language is English. Worse, if you are already logged into Audible, the extension cannot recognize this. And finally, if you really are in some other country, the Audible.[country-code] site you will probably be using does not actually share account data with Audible.com anyway. E.g., I was using a VPN that showed me being in Canada, and Audible.com forcibly redirects such IP addresses to Audible.ca; while my Amazon & Audible login credentials worked there (through Amazon.ca), my Audible.ca account was empty and showed none of my Audible.com library contents. So, jumping through VPN hoops to use Audible.de and (for login auth) Amazon.de simply isn't going to work.
This addon appears to be for no one but Germans in Germany who use (and only use) Audible.de and Amazon.de, and who are fond of using English-language interfaces for no particular reason, and who are webmasters of websites they can auto-upload to through a Firefox addon, but who also don't care about passwords being sent in the clear to that site they run. Maybe that's a target market of ... half a dozen people?
All that said, the bare guts of this are probably functional, and with not-very-complicated work it should be viable. It needs to: 1) support whatever amazon.[tld] and audible.[tld] site you actually need; 2) stop asking for access to every website; 3) default to saving files locally (either by picking a location with standard UI widgets, or entering a file:/// path); and 4) only ask for a remote upload host if someone wants that (then add that host to the sites it has permission to access, and treat ID and PW info securely).
Audible Backup requires some risky permissions and may not be safe to use. Exercise caution
when installing this add-on. Review carefully before installing.
Risk impact measures the level of extra permissions an extension has access to. A low risk impact
extension cannot do much harms, whereas a high risk impact extension can do a lot of damage like
stealing your password, bypass your security settings, and access your personal data. High risk
impact extensions are not necessarily malicious. However, if they do turn
malicious, they can be very harmful.
Risk likelihood
Audible Backup has earned a fairly good reputation and likely can be trusted.
Risk likelihood measures the probability that a Firefox add-on may turn malicious.
This is determined by the publisher and the Firefox add-on reputation on Firefox Browser Add-ons,
the amount of time the Firefox add-on has been around, and other signals about the
Firefox add-on. Our algorithms are not perfect, and are subject to change as we
discover new ways to detect malicious extensions. We recommend that you always exercise caution
when installing a Firefox add-on, especially ones with higher risk impact and/or
higher risk likelihood.