The simple_captcha2 gem 0.2.3 for Ruby, as distributed on RubyGems.org, included a code-execution backdoor inserted by a third party.
https://rubygems.org/gems/simple_captcha2/versions/
https://github.com/rubygems/rubygems.org/issues/2073
https://snyk.io/vuln/SNYK-RUBY-SIMPLECAPTCHA2-455501
Source: Mitre, NVD
Published: 2019-07-26
Updated: 2026-06-17
Base Score: 7.5
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P
Severity: High
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity: Critical
EPSS: 0.01431