[gamaken]

I have a quick fix for preventing all post (and/or sig) images opening in new tabs.
Change:

$post['message'] = str_replace('<img', '<img style="max-width: ' . $this->registry->options['gquick_autoresize_maxwidth'] . 'px; cursor: pointer;" onclick="window.open(this.src)" ', $post['message']);

To:

$post['message'] = str_replace('<img', '<img style="max-width: ' . $this->registry->options['gquick_autoresize_maxwidth'] . 'px; " ', $post['message']);

For signatures....
Change:

$post['signature'] = str_replace('<img', '<img style="max-width: ' . $this->registry->options['gquick_autoresize_maxwidth'] . 'px; cursor: pointer;" onclick="window.open(this.src)" ', $post['signature']);

To:

$post['signature'] = str_replace('<img', '<img style="max-width: ' . $this->registry->options['gquick_autoresize_maxwidth'] . 'px; "  ', $post['signature']);

That fixes the problem, but in order to see a full size image you have to middle mouse or right-click to open, which for me was a good trade-off.