Medium · published January 17, 2024
flaskBlog is a simple blog app built with Flask. Improper storage and rendering of the `/user/<user>` page allows a user's comments to execute arbitrary javascript code. The html template `user.html` contains the following code snippet to render comments made by a user: `<div class="content" tag="content">{{comment[2]|safe}}</div>`. Use of the "safe" tag causes flask to _not_ escape the rendered content. To remediate this, simply remove the `|safe` tag from the HTML above. No fix is is available and users are advised to manually edit their installation.