Error Saving: Possible hack?

I keep getting this message of late: 

Error Saving: Your changes conflict with a newer version of this document. Your changes here will not be saved.

According to Squarespace, it's due to multi-contributors or the same page opened elsewhere. 

But I don't have co-contributors and I don't have another page open. 

Is this pointing to a security hack?  Or is this a wonky Squarespace thing?

It's difficult for anyone other than Squarespace engineers to tell you why this is happening in your particular circumstances. I'm a heavy Squarespace user on notebooks and desktops working on different networks and I've only ever seen this issue when there are multiple contributors posting conflicting saves, or when the same site was opened on multiple tabs or multiple computers.

If you are the owner and there are no other contributors then I recommend checking your browser is up to date and if yes, clearing your browser's cache. If you have further problems, reach out to Squarespace Customer Care again.

In addition to @paul2009's excellent advice it wouldn't hurt to quit out of your browser and also restart your machine. Get a fresh start with everything! 🙂