Open redirect protection (https://www.pixiv.net/jump.php) is broken for novels

How it was found

Summary:

I found that pixiv has a open redirect protection, any external link in illustration is converted to https://www.pixiv.net/jump.php?<link provided by user>. For example https://i3mx4usociis8twimpcu2ty0erkh86.burpcollaborator.net/abc in https://www.pixiv.net/member_illust.php?mode=medium&illust_id=74148892 is converted to https://www.pixiv.net/jump.php?https%3A%2F%2Fi3mx4usociis8twimpcu2ty0erkh86.burpcollaborator.net%2Fabc. See the attachment "illust.png".

However, that is not true for novels. Links in novel is shown to be converted to jump.php link in preview (see attachment "preview.png") but they actually aren't. See https://www.pixiv.net/novel/show.php?id=109971051 and "novel.png" for an example.

Since the "jump.php" protection mechanism is working for illusts and the preview of novels, I think lacking this protection for novels is not an intended behavior.

Steps To Reproduce:

1. Add a novel
2. Choose "Add URL" and edit the content to something like [[jumpuri:https://pixiv.net/ > https://i3mx4usociis8twimpcu2ty0erkh86.burpcollaborator.net/abc]]
3. Save
4. You will see a link in the novel which reads https://pixiv.net/ but actually it is https://i3mx4usociis8twimpcu2ty0erkh86.burpcollaborator.net/abc. See https://www.pixiv.net/novel/show.php?id=10997105 for your reference.

Impact

Faking users to the wrong site