Mortgage rates moved slightly higher over the past two days as strong economic data and corporate earnings coaxed investors into riskier assets like stocks. Bonds (which dictate interest rates) are always being bought and sold, but demand varies depending on investors' risk appetite. If demand for bonds falls as it has in the 2nd half of this week, rates move higher.
Fortunately, this move has been very small in the bigger picture. Mortgage rates, specifically, have moved even less than rates associated with other bonds. The average lender is still able to offer 30yr fixed rates of well under 4% on top tier scenarios. And the average borrower wouldn't see more than 0.00125% of difference from the lowest rates in more than 3 months. Bottom line, while rates are slightly higher than their best recent levels, you'd have to go back to early October or before to see anything significantly better.