You are a company publication professional and have been supporting authors to develop an oral presentation for a scientific congress. The content is agreed upon and approved by authors prior to the start of the congress. Both sponsor and medical writing agency colleagues are onsite to provide support, and it was agreed that the presenting author would upload the slides to the system. Approximately 2 hours before the presentation, you see the presenting author, who mentions that he/she reviewed the slides again, changed them, and then uploaded them without obtaining further approval from the co-authors.
What would you do?