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I am researching some security bugs within some websites and would like to know if jinja2 enables autoescape by default. According to the Jinja documentation (http://jinja.pocoo.org/docs/2.9/faq/#why-is-autoescaping-not-the-default), it doesn't, but while I was testing the app on a new system, it was enabled (I may have accidentally done that though, not sure.

Can anyone shine some light on this?

Answers

According to the flask documentation:

Unless customized, Jinja2 is configured by Flask as follows:

autoescaping is enabled for all templates ending in .html, .htm, .xml as well as .xhtml when using render_template().

Also:

autoescaping is enabled for all strings when using render_template_string().

Finally:

a template has the ability to opt in/out autoescaping with the {% autoescape %} tag.

So, while jinja may not autoescape by default, flask turns on Jinja's autoescaping by default.