Those brown spots are probably from the Manufacturing process. You can use 92% Isopropyl Alcohol and carefully see if you can clean it off. Install the Ryzen and see if it boots up and everything works correctly.
Found this previous Tom's Hardware thread that explains this: Just got my NEW Ryzen 5 2600 from newegg, has brown/clear spots on it? | Tom's Hardware Forum
The answer from this User seems to be someone experienced with Computers and I also tend to agree with him.
But if you want to feel better about those spots open a AMD WARRANTY REQUEST ticket and ask them to verify the above information from here: https://www.amd.com/en/support/kb/warranty-information/rma-form
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