What happened if the third author made extensive changes for galley proof without letting the editor, first and corresponding authors know? One of the papers (Letter to the Editor) I am first authors got accepted with no revision, and it is in under the proofing system now. The publisher gave us 48 hours to revise but somehow the third author just bounced up in the last hour to change and paraphrase almost every single sentence and add a reference without previously letting both the corresponding author and me know. When I found out, I was just OK with it, but I required her to contact the editor for approval before submitting the paper or made any change. Now the second author of the paper just rushed and submitted the revised version without anyone else's agreement although I had kept telling him not to do so.

I particularly concern that this is very unacceptable behaviour and moreover I have other two first-authored papers under the review in the same journal. Will this have any impact on my other papers? Did anyone experience the same thing before? Is making 30+ changes considered extensive changes?
I think you can relax - this isn't that big a deal.

You can contact the editor / publisher and say there has been a miscommunication between the authors, and you need some more time to sort it out and make sure that everyone approves the edits.  I imagine this sort of thing must happen all the time.  In the worst case, the paper might have to be postponed to a later issue, which is a little annoying but still better than having some authors be unhappy with the final version.


  I particularly concern that this is very unacceptable behaviour


I wouldn't say that - more of a minor error or misunderstanding.  Yes, the other authors should have been more careful about seeking everyone's approval, but under time pressure people sometimes make shortcuts or false assumptions.  Just sort it out and ask them nicely to pay more attention in the future - don't let something this minor ruin your working relationship with them.


  Will this have any impact on my other papers? 


That seems extremely unlikely.


  Is making 30+ changes considered extensive changes?


The number of changes isn't really relevant - it's about quality, not quantity.  Do the changes significantly affect the content of the paper, such that a reviewer might need to reconsider whether the paper can still be published?  Changes such as paraphrases and added references shouldn't reach that level, even if there are a lot of them.