There is XSS vulnerability when loading content which was fixed for Quill 2.x in https://github.com/quilljs/quill/pull/2226. Would it be possible to include the patch in 1.x to prevent being vulnerable for users on the stable release?
The issue you linked specifically was also introduced in 2.x
I believe a similar issue is present in 1.x. Here is a codepen demonstrating XSS with Quill 1.3.7.

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I believe a similar issue is present in 1.x. Here is a codepen demonstrating XSS with Quill 1.3.7.