Corrupted Content error when using uMatrix with Firefox on discourse forum websites

[sloxy]

Prerequisites

• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
  • Your issue may already be reported.
  • I also searched the existing issues at https://github.com/gorhill/uMatrix/issues
• This is not a support issue or a question
  • Support issues and questions are handled at /r/uMatrix
• I tried to reproduce the issue when...
  • uMatrix is the only extension
  • uMatrix with default lists/settings
  • using a new, unmodified browser profile
• I am running the latest version of uMatrix
• I checked the documentation to understand that the issue I report is not a normal behavior
• I used the logger to rule out that the issue is caused by my ruleset

Description

When uMatrix is installed & enabled, Firefox starts having "Corrupted Content" error when visiting site.
When uMatrix is not installed, this does not happen.
When uMatrix is installed but the global (*) is not enabled, this does not happen.
When uMatrix is installed, the global (*) is enabled, but site rule is not enabled, this does happen.

A specific URL where the issue occurs

clojureverse.org

Steps to Reproduce

1. Open Firefox, Install uMatrix
2. Visit clojureverse.org
3. See error

Supporting evidence

youtube video of new profile in firefox without issue occurring, then umatrix installed & error occurs: https://youtu.be/1ap_Fx3IK_8

discussion on Discourse forum where other sites and users are experiencing it along with some other thoughts from users: https://meta.discourse.org/t/firefox-experiences-network-protocol-violation-on-discourse-based-websites/97308

screenshot of error:

also opened bug against Firefox : https://bugzilla.mozilla.org/show_bug.cgi?id=1502606 as this issue does not occur in Chrome on Windows with uMatrix

Your environment

• uMatrix version: 1.3.14
• Browser Name and version: 63.0
• Operating System and version: Windows 10, version 1803

[sloxy]

some other affected sites which I could reproduce against are:
https://elixirforum.com
https://meta.discourse.org/
https://community.freepbx.org/

[gorhill]

[ Y] I performed a cursory search of the issue tracker to avoid opening a duplicate issue

Duplicate of #72.

[sloxy]

apologies. i had looked through the open issues and couldn't see it (i can see it's now closed and in RC for next version)

👍

have tried upcoming RC 1.3.15rc1 and looks like that solves my issue.