"Your submission could not be processed because a security token was missing."

[Angel-Wings]

That's a style based error and it can be fixed within some minutes

Open in your AdminCP the "Styles & Templates" and search for "profile.php" in the Default Template - looks like:

<!-- auto DST correction code -->
<form action="profile.php?do=dst" method="post" name="dstform">
<input type="hidden" name="s" value="$session[sessionhash]" />
<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" />
<input type="hidden" name="do" value="dst" />
</form>

Then copy & paste this and replace it in the same Template in the Style causing the problem.

The "footer" templates usually cause this problem so it should be there. And - usually - the important line.

<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" />

is missing so the redirection creates an error message.