Stock buyback programs are typically viewed positively by the market as they can indicate that a company believes its stock is undervalued and that it is confident in its financial stability. Reaffirming guidance suggests that the company's performance is on track, which can also be reassuring to investors. The appointment of an interim COO may be seen as a step towards strong operational leadership, although it may have a less direct impact on the stock price than the buyback program and guidance.