As a PC member, you are responsible to protect the confidentiality of the ideas and work represented in the paper(s) that you have been assigned.
Do not show the paper to anyone else, including colleagues or students, unless you have asked them to write a review, or to help with your review. You could include them as external reviewers as they should be recognized. However, you are ultimately responsible for the papers being assigned to you.
As a reviewer of WSDM papers, you are expected to uphold professionalism and integrity to the highest level in your objective and unbiased review of the papers. It is important for you to avoid any real and perceived conflict of interest. Hence, if you are assigned a paper where you review would create a possible conflict of interest, you should return the paper and not submit a review. Conflicts of interest include (but are not limited to) situations in which:
In connection with any actual or possible conflict of interest, an SPC, a PC member, or a Reviewer must disclose the existence of any potential conflicts with the Program (Co-)Chairs.
The Program (Co-)Chairs will make the final decision on whether there exists a conflict of interest.
The General (Co-)Chairs will make the final decision in the case of COI with the Program (Co-)Chairs.