It depends on your basis in the stock and how long you've held the stock. If you have had it over a year, the gains are long-term capital gains. Stock you have owned less than a year is short-term and taxed at the same rate as ordinary income.
Example: If your basis in the stock is $15K, you would have a gain of 10K, and if that gain is long-term, you would still be at the 0% capital gain rate for that income. However, the $10K would increase your total income, which would make more of your social security taxable.
**Say "Thanks" by clicking the thumb icon in a post**Mark the post that answers your question by clicking on "Mark as Best Answer"