Stored XSS in October

Impact

A user with access to a markdown FormWidget that stores data persistently could create a stored XSS attack against themselves and any other users with access to the generated HTML from the field.

Patches

Issue has been patched in Build 466 (v1.0.466) & RainLab.Blog v1.4.1 by restricting the ability to store JS in markdown to only users that have been explicitly granted the backend.allow_unsafe_markdown permission.

Workarounds

Apply https://github.com/octobercms/october/commit/9ecfb4867baae14a0d3f99f5b5c1e8a979ae8746 & https://github.com/rainlab/blog-plugin/commit/6ae19a6e16ef3ba730692bc899851342c858bb94 to your installation manually if unable to upgrade to Build 466 or v1.4.1 of RainLab.Blog (if using that plugin).

References

Reported by Sivanesh Ashok

For more information

If you have any questions or comments about this advisory:

• Email us at [email protected]

Threat assessment:

<img width=“1100” alt=“Screen Shot 2020-03-31 at 2 01 52 PM” src=“https://user-images.githubusercontent.com/7253840/78070158-8f7ef580-7358-11ea-950c-226533f6a0a3.png”>