Arabic footnotes in tcolorbox

Question

If I use a \footnote command in tcolorbox the footnote will be alphabetically numbered. Question: How do I change this to arabic numbering?

I've tried \renewcommand{\thefootnote}{\arabic{footnote}}, but that didn't work out. And the manual does not even mention the footnote changes.

MWE:

\documentclass{article}
\usepackage{tcolorbox}
\begin{document}
\begin{tcolorbox}
    \renewcommand{\thefootnote}{\arabic{footnote}}
    Some footnotes\footnote{Test} should be represented by an arabic number\footnote{Test}
\end{tcolorbox}
\begin{tcolorbox}
    Some footnotes\footnote{Test} should be represented by a letter\footnote{Test}
\end{tcolorbox}
\end{document}  

Answer 1

The usage of \alph instead of \arabic is no documented feature and only looking into tcolorbox.sty gives some insight about the proceedings in the package:

The counter used in tcolorbox boxes for footnotes is not footnote but mpfootnote (where mp is short for minipage) and \thempfootnote must be changed accordingly.

By default, in latex.ltx, \thempfootnote comes down to \alph{mpfootnote} effectively, i.e. using lower case letters for 'numbering' the footnotes, so the effect is the 'fault' of the LaTeX core itself.

\documentclass{article}
\usepackage{tcolorbox}
\begin{document}
\begin{tcolorbox}
  \renewcommand{\thempfootnote}{\arabic{mpfootnote}}
    Some footnotes\footnote{Test} should be represented by an arabic number\footnote{Test}
\end{tcolorbox}
\begin{tcolorbox}
    Some footnotes\footnote{Test} should be represented by a letter\footnote{Test}
\end{tcolorbox}
\end{document} 

Here's a version with code= key and definition of a special box for arabic footnotes:

\documentclass{article}
\usepackage{tcolorbox}

\newtcolorbox{footnotebox}[1][]{code={\renewcommand{\thempfootnote}{\arabic{mpfootnote}}},#1}


\begin{document}
\begin{footnotebox}
    Some footnotes\footnote{Test} are represented by an arabic number\footnote{Test}
\end{footnotebox}

\begin{tcolorbox}
    Some footnotes\footnote{Test} should be represented by a letter\footnote{Test}
\end{tcolorbox}
\end{document}