First author added random co-authors to our paper without informing me (second author) Our paper in the computer science area has been accepted to a well-known conference and we are getting ready to submit our final draft. This is our first publication and I'm an undergraduate student.

The first author of this paper added 2 extra random people to the co-authors list for revising and proof checking the paper. I'm the second author and I wasn't made aware of this at all and I found it as I was getting ready to edit the paper. They didn't make a significant contribution to the content/material of the paper. Before the 2 people were added, we already had 6 people on the list: 3 students and 3 professors.

Now there are 8 authors and I'm concerned whether my work and the effort I put in will be diluted because of more authors. I don't want it to cheapen the paper. I talked to the first author and he's being stubborn that they deserve to be on the list and isn't interested in changing the list. Should I discuss it with our professors or is it not worth the time and effort? I'm interested in obtaining a PhD and I don't want the additional authors to negatively affect the way my contribution is seen by graduate schools.
There are a lot of different issues here so let me try and unpack them a bit.

First of all, it is not ok for your coauthor to add others to the paper without your consent (or that of everyone involved for that matter). This is especially true if the paper has already been accepted for publication. In fact, some conferences expressly forbid this practice as it can lead to very bad behavior on the authors’ side as was noted in the comments. I would check the conference submission guidelines to make sure your coauthor isn’t violating them.

Should you consult your fellow coauthors on this? I think so. The criteria for coauthorship can vary widely across disciplines and labs. My personal view is that proofreading doesn’t warrant it, but that may depend on its extent. I honestly doubt that two people had so much to contribute that they had to be added as coauthors in the last minute, but I could be wrong (it is very weird though).

What can you do about it? Your options are are basically getting other coauthors to support your claim, and having a conversation about the new authors’ addition. Your nuclear option is to contact the conference chairs and inform them. This alternative, however, has a very good chance of having the paper withdrawn from the conference altogether. If you’re interested in joining graduate school then this is not a good idea (though it is arguably the ethical thing to do). Remember, you could also just flat out say that you’re not willing to have the paper published with their names on it (if one coauthor objects the paper can’t be published), but you’ll be burning bridges if the professors on the papers don’t have your back.

What should you do? If you want to get into graduate school then swallowing this ethical pill is your best bet. I’m guessing this was something your coauthor banked on when they pulled this stunt. Try to chat with your professors and see what they think, maybe you can figure it out.