BUG (?): Blue box around Pie / Donut chart segment

[skuske]

Sometimes a blue selection box appears around a pie/donut diagram when you select it with your finger. I can't say exactly how to reproduce this 100%, but some touches with the finger provoke the appearance of this blue box. This is extremely annoying as users do not understand the purpose of this box. How can I prevent this box from appearing? The problem exists with every Pie / Donut Chart, including the iOS demos.

I am not using the accessibility module / plugin.

I urgently ask for help!