tcolorbox and footnote marks

Question

I want to change the default footnotemark style inside a tcolorbox, but using \renewcommand{\thefootnote}{\fnsymbol{footnote}} in the preamble does not work.

The tcolorbox is inside an environment created with \newenvironment. I have tried putting \renewcommand{\thefootnote}{\fnsymbol{footnote}} inside its definition, but still doesn't work.

I have searched inside the tcolorbox manual, but I can't find nothing about that.

Here's a MWE:

\documentclass[12pt]{article}
\usepackage{tcolorbox}

\newcounter{problem}[section]
\def\theproblem {\arabic{problem}}
\def\problem{%
    {\par{\makebox[1.8em][l]{\large\bf\theproblem.~}}}
}

\newenvironment{Exercise}
    {
        \refstepcounter{problem}
        \renewcommand{\thefootnote}{\fnsymbol{footnote}} %This doesn't work:(
        \begin{tcolorbox}[]
        \noindent\problem{}
    }
    {
        \end{tcolorbox}
        \smallskip
    }

    \begin{document}
            \begin{Exercise}
                An exercise\footnote{This is the footnote} with a footnote.
            \end{Exercise}
    \end{document}

and the typeset:

Any help?

Answer 1

What I meant is:

\documentclass[12pt]{article}
\usepackage{tcolorbox}
\newtcolorbox[auto counter,number within=section]{Exercise}[1][]{%
before upper=\renewcommand\thempfootnote{\fnsymbol{mpfootnote}},
title=Problem \thetcbcounter}
\begin{document}
\section{Pft}
\begin{Exercise}
    An exercise\footnote{This is the footnote} with a footnote.
\end{Exercise}
\end{document}

What is important here is that you were modifying the wrong mark, in minipages you need to use mpfootnote.. Applying this to your MWE (thanks BTW!) yields

\documentclass[12pt]{article}
\usepackage{tcolorbox}

\newcounter{problem}[section]
\def\theproblem {\arabic{problem}}
\def\problem{%
    {\par{\makebox[1.8em][l]{\large\bf\theproblem.~}}}
}

\newenvironment{Exercise}
{
    \refstepcounter{problem}
    \renewcommand{\thempfootnote}{\fnsymbol{mpfootnote}} %This doesn't work:(
    \begin{tcolorbox}[]
    \noindent\problem{}
}
{
    \end{tcolorbox}
    \smallskip
}

\begin{document}
        \begin{Exercise}
            An exercise\footnote{This is the footnote} with a footnote.
        \end{Exercise}
\end{document}