If you received an SMS message from Safaricom stating that "Safaricom is updating M-PESA Menu to enhance your experience..." then you should not be worried as it only involves updating the Safaricom menu journey. The most important thing is don't enter your mpesa PIN.
Just click OK and you are safe. No none can get money out of your Mpesa account unless you enter your PIN.
Message from safaricom;
"Dear Customer, Safaricom is updating M-PESA Menu to enhance your experience. You will receive a prompt on your phone. Click OK to accept. NO PIN is required"
Important! Please be aware that scammers will take advantage of the situation and start initiating Mpesa payment prompts. We want to emphasize again that you should not enter your Mpesa pin to update the menu.