CVE-2021-39197

bettererrors is an open source replacement for the standard Rails error page with more information rich error pages. It is also usable outside of Rails in any Rack app as Rack middleware. bettererrors prior to 2.8.0 did not implement CSRF protection for its internal requests. It also did not enforce the correct "Content-Type" header for these requests, which allowed a cross-origin "simple request" to be made without CORS protection. These together left an application with bettererrors enabled open to cross-origin attacks. As a developer tool, bettererrors documentation strongly recommends addition only to the development bundle group, so this vulnerability should only affect development environments. Please ensure that your project limits bettererrors to the development group (or the non-Rails equivalent). Starting with release 2.8.x, CSRF protection is enforced. It is recommended that you upgrade to the latest release, or minimally to "~> 2.8.3". There are no known workarounds to mitigate the risk of using older releases of bettererrors.