same as me
it did work yesterday but now I cannot connect to webdav based 4shared

Same with me. I have been working with 4shared for about a year and I never encountered any such problem. It all started from yesterday. Don't have any clue what's happening.

Yep, and looks like that attack was specifically related to WebDAV:

https://www.bleepingcomputer.com/news/security/bumblebee-malware-returns-in-new-attacks-abusing-webdav-folders/

If you're experiencing this, you'll need to ask 4shared for any updates. This isn't a problem in Zotero itself, and there's no need for further posts saying that it's happening to you.

@kwmullet: That's absurd. Zotero works with every properly functioning WebDAV server that exists. If your WebDAV provider is rejecting valid WebDAV requests or otherwise doing something bizarre and nonstandard, that's obviously not a problem in Zotero. Complain to them, pick a different provider, or use Zotero Storage, but there's nothing for us to do here.

(And while I have no information on what happened here, I suspect you're confused about this. 'zotero' is a folder on the WebDAV server. It has literally nothing to do with HTML, so it would make no sense for there to be an .html extension anywhere.)

I just switched to Infinicloud. https://infini-cloud.net/en/

They seem to me to have 20G of free cloud storage that seems to work for my Zotero clients. Once you create (what seems to me to be) a free account, go to the "My Page" link from the top right ID drop down menu. Turn on Apps Connection to enable Webdav. You'll get a connection URL to use in your Zotero sync configuration as well as a connection userid and Webdav password. You'll need to save that password somewhere, because once you leave that screen, it won't display again, so you'll have to generate a new one if you lose it.

That setup passed the "verify server" test in Zotero settings, but I further found that it seemed to be necessary for me to force a webdav sync. What I did that seemed to work was to go to settings, sync, show reset options (at the very bottom), and choose "Reset File Sync History" which will force Zotero to compare all local and remote attachments and reconcile them.

Once I did that, I selected the circular arrow from the top right of the main window to start a sync, it took quite a while, but everything seems to be great now.

@xxtraloud,

I can't speak to the comparative technical merits of WebDAV v. FTP. I suspect WebDAV has versioning and updating features that aren't present in FTP. I likewise suspect that since WebDAV takes place within a single socket (typically tcp/80 or tcp/443) not separate control and data sockets as does FTP, it's easier to manage with regard to firewalling and traffic control. My impression from the tone of his latest message is that @dstillman is both an authority on WebDAV as well as one of the developers on the Zotero project, so I'd direct you to him for authentic detailed information.

From a broader perspective, and within the context of Zotero, I think that Zotero does back-end remote file syncing with WebDAV while it doesn't do it with FTP, so to my mind, it doesn't so much matter if one is technically better (I think WebDAV is) or more widely-supported (certainly FTP is) than the other. WebDAV is what Zotero uses and we're using Zotero.

Same problem here. I noticed that when trying to login directly to webdav.4shared.com my credentials fail, despite working on www.4shared.com. Was anyone using 4shared been able to restore webdav access to 4shared / Zotero synching using it?

Hope you are all well.

@subrata001 "Maybe 4shared disabled WebDAV access for free users (?)."
No. Zotero still provides WebDav access to free users. The problem is more related to 4shared being under attack by a ransomware and you can find the same error if you try to access the network location of 4shared webdav folder from "This PC" on windows.

The problem is not only limited to syncing new items but there are also problems for old pdfs and file attachments which will not open showing an error message of not being able to locate files (meaning the loss of access to files and comments/annotations within them!). Still, thanks to Zotero syncing of standalone and item notes to its own cloud service without size limitations, those notes and details of items citations are still intact.

Other cloud services with WebDAV are working fine. Zotero developers are really generous in providing this WebDAV alternatives for those who cannot pay for Zotero cloud subscription (although it is highly reasonable) and still need to sync their libraries online.

Thanks @dstillman and @adamsmith for clarifications, thanks for pinning the news about 4shared so that all concerned users can take their caution, and thanks @kwmullet for the suggested alternative ( Infinicloud) and his detailed description of a feasible solution. I believe to save the files (and their comments and annotations) you will need a machine with a local library with most recent changes that has not been synced yet with 4shared in the last days (before the attack on 4shared ) or to search for the local library and make a backup copy of it, then you will need to follow the steps suggested by @kwmullet (adding the new webdav credentials , choosing reset, and syncing everything again, and repeating these steps on all your machines as well).

Best wishes and regards for all

Same problem here.

Folks, there's no point in posting just to say you're affected by this. This isn't a problem in Zotero, and we have nothing to do with 4shared. If you're having trouble with a given WebDAV provider, your options are to contact the provider for help, switch to a different WebDAV provider, or use Zotero Storage, which always works.

I'm going to close this thread now. There's no point posting about this further here — this is a problem with 4shared and has nothing to do with Zotero. If you're affected by this, see my previous comment for your options.