What to do about advisor with history of possible plagiarism? Recently, my MS advisor instructed me to submit a conference paper.  They outlined what this paper would include, which would be a simulation study that is a near duplication of a ten-year-old published journal article (from a different group of researchers) that I have been reproducing results from for learning purposes.  They said to omit citation of that journal article for the initial submission, and add it in the final draft if the conference paper is accepted.  From a professional integrity standpoint, I have no intention to do this.  I plan to write a paper that extends the results, and to include the citation in all drafts.  I am unhappy that my advisor instructed me to essentially plagiarize, but plenty capable of not doing so, so I wasn't going to make a fuss about it.

However, in my literature search for writing my conference paper, I stumbled across Paper A that is extremely similar to one of my advisor's papers, Paper B.  Paper A has different notation, but the same equations and results, published about 30 years earlier than my advisor's paper.  Paper B does not cite this older paper, but does include a new simulation example in additional to the similar material, so it is not a complete copy.  In light of their recent request to me, I am suspicious of my advisor's previous publications, and uncertain how to proceed working with them.

Should I show this older paper to them and ask about it?  Should I report this to some higher authority?  Is this a relatively common occurrence that I am overthinking?  I do not rely on my advisor for funding, but I would not be thrilled about sabotaging my thesis by starting drama with my advisor.  I would also not be thrilled to sabotage my future publishibility by working with a serial plagiarizer.
First, don't assume that it is plagiarism without more evidence. Parallel research is very common in many fields and a 30 year old paper may not have been well known in the time frame your professor wrote his/her paper. It may well be plagiarism, but it isn't necessarily so. 

It is appropriate to point out the newly found paper to your advisor and gauge the reaction, but it is premature to "complain" to higher authority without solid evidence. You are correct to be wary. But showing it to your advisor could be just an "oh by the way, I came across...". Depending on the reaction you may learn more about their general attitude. 

It would, indeed, be unfortunate to have to work with someone with poor ethical standards and if your suspicions are verified you might try to move to a different advisor. This is less critical at the MS level than it would be later, but as long as you preserve your own ethical reputation, you should be fine. 

But, certainly, the recent instructions about omitting a reference are problematic. It is possible to write a valid paper reproducing and verifying old results without crossing ethical boundaries. But the work clearly needs to be presented that way, rather than as an innovation. If the referees are up to date in the field, such obfuscation may be caught to everyone's detriment.