The ICMJE guidelines on the role of authors and contributors explicitly state that the final approval of all co-authors should be taken before submitting a manuscript. Since you are the corresponding author, there is no way the paper can be submitted without your knowledge, which is why probably you came to know about the change. Your collaborator should have discussed with you and the first author before including the name of the other student in the paper. However, since the revised paper has not yet been submitted, you can still discuss and include the second student only if all the co-authors agree to this.
The ICMJE guidelines also state that in order to qualify for authorship, a contributor must have done all of the following:
- substantially contributed to conception and design, acquisition of data, or analysis and interpretation of data
- drafted the article or revised it critically for important intellectual content, and
- provided final approval of the version to be published.
- agreed to be accountable for the work.
On the basis of the second of the above points, even if the student was not involved in the first draft, he/she might qualify to be a co-author if the reanalysis he/she has done is of substantial intellectual significance. You and your other co-authors will have to assess whether the reanalysis adds enough value to the paper to merit authorship. If not, you could mention the student's contribution in the acknowledgements section.
The paper cannot be published unless all of you give your approval. If you feel that your collaborator can go ahead and submit the revised paper with the student as a co-author without your knowledge and approval (which is unlikely since you are the corresponding author), you should keep the editor informed of your disagreement beforehand.
- Does someone who has assisted in experiments qualify to be a coauthor?
- Who can be included as a co-author of a paper?
- Can I submit a paper without informing my co-author?