TYPO3 Core

When using the extension manager to install a lower version of an extension, which is not compatible with the current TYPO3 version, a warning is shown that dependencies could not be resolved. The user gets prompted to either cancel the installation or to proceed. In the background the lower version of the extension gets already installed, when cancelling the process the lower version is installed without the user knowing.

• install compatible extension (e.g. gridelements 7.2.0) through extension manager
• open extension manager, go to "Get Extensions" and choose to install an incompatible version of the extension (e.g. gridelements 3.4.0)
• Cancel the "dependencies could not be resolved" warning
• check the installed version of the extension in the extension manager

Tested on:
TYPO3 7.6.24
TYPO3 8.7.10

When installing an incompatible extension for the first time, cancelling actually cancels the process and the extension is not installed. This would be the expected behaviour when cancelling the installtion of a lower version as well.