This extension is published under the Mozilla Public License, an open source license, and the code repository is at https://github.com/jscher2000/Save-webP-as-extension/. You also can review the code by right-clicking the "Add to Firefox" button and using Save Link As. The .xpi file is a ZIP archive, so you can extract it and read the files locally.

The reason such broad permissions are required is that many images are hosted on a different server, and Firefox doesn't provide a convenient way to prompt for permission to operate on embedded cross-site content. Maybe I can make a lower-permission version that only works with stand-alone images?

If you prefer an extension-free approach, you can emulate the way this extension works using Firefox's built-in screenshot feature. That usually downloads in PNG format, but occasionally it may use JPEG format.

If you go to the Options for the add-on (click the "gear" wheel icon on the button bar), "Save Path Options" section, you can change to saving directly in the Downloads folder. Due to limitations on where add-ons can auto-save, I can't offer very much flexibility on this. If you prefer to choose where to save each time, the setting above that lets you select your preferred approach.

Hi, do you mean the one assigned CVE-2023-4863? Mozilla issued Firefox 117.0.2 and 115.2.1 to address the problem. See: https://www.mozilla.org/security/advisories/mfsa2023-40/

The reason for mentioning that patch is: this extension uses features Firefox makes available to add-ons and web page scripts; the extension does not have its own image conversion libraries.

I know, it's inconvenient and demands a lot of trust. This add-on only reads data when you call it up, and it does not read data in pages other than the image it's operating on. Either way, it doesn't send info to me -- I have no interest what is happening in anyone else's browser.

For what it's worth, I did *try* to write this extension *without* that permission. If the image is hosted on the same server as the page (both the same server as listed in the address bar), then the fact that you right-clicked the image could grant one-time permission automatically (so called activeTab permission).

But a large proportion of images are hosted on a different server, so that method failed frequently in real world testing. Maybe there is a new solution to this four years down the road? I'll update this reply if I find one and rewrite the add-on.

Apologies for overlooking your review when you posted it. If this error still appears in version 1.4, can you share the URL of the page with the problem image(s), either here or on Github at https://github.com/jscher2000/Save-webP-as-extension/issues or by email at jscher2000@outlook.com.

(1) Set up one-click saving

Instead of having to click a second button to convert an image, you can set up one-click saving in the add-on options -- check out the following screenshot -- by changing the "Plain click" action to whichever quality of JPEG you prefer:

https://addons.mozilla.org/user-media/previews/full/255/255669.png

(2) Where to save (or to always ask)

Add-ons can only auto-save within your default downloads folder. So far, I've created a couple options for how to set up the folder path, which are also in the add-on options. At some point, I do want to add more possibilities there.

To change from auto-save to showing the Save As dialog: click the Options (gear) button, and under "Show Save As dialog each time" click the Yes bubble.

Could you let me know the site where you don't get a useful file name? I'm not sure the add-on can detect the intended name, but I can take a look. (You can contact me at jscher2000@outlook.com or using the Support link on the main page.) You also could try using the IE11 button in those cases -- it doesn't change the format, but modifies the request to the server to try to get whatever format they offer to older browsers.