https://www.yiiframework.com/news/178/yii-1-1-20-is-released

This release is a maintenance release of Yii 1.1.x which contains compatibility fixes for PHP 7.0 and 7.1.

See the complete release announcement for all details:
https://www.yiiframework.com/news/137/yii-1-1-19-is-released/

This release is a maintenance release of Yii 1.1.x which contains compatibility fixes for PHP 7.0 and 7.1.

See the complete release announcement for all details:
https://www.yiiframework.com/news/133/yii-1-1-18-is-released/

This is the last release of Yii 1.1.x containing Enhancements.
Future releases will be bugfix only.

See the complete release announcement for all details:
https://www.yiiframework.com/news/93/yii-1-1-17-is-released/

In this release, we fixed more than 120 enhancements and bug fixes.

See https://www.yiiframework.com/news/83/yii-1-1-16-is-released/ for the complete release news.

This release fixes a security issue found in CDetailView in the 1.1.14 release. The issue allows an attacker to
potentially execute arbitrary PHP script on the server. So we urge all 1.1.14 users to upgrade Yii to this latest release. Note that the issue only affects 1.1.14. All previous releases are not affected.

Upgrading to this release is very safe and will not break your existing code.

We have reserved a CVE number (CVE-2014-4672) for this issue that you can use to refer to it.

https://www.yiiframework.com/news/78/yii-1-1-15-is-released-security-fix/

Please download 1.1.15 instead. This version contains a security issue that was fixed in 1.1.15.

• Fixed more than 80 bugs
• Introduced more than 60 minor enhancements and features
• Added CPasswordHelper that provides secure and up to date way to store and verify password hashes.
• Added CRedisCache to support using Redis for caching purpose
• Yii can now be installed as a Composer package

More details can be found in the release news.