Function getOldManifest searched invalid path. It relied on extension_administrator path, which is available only for components. Changed to extension_root, which is available for all extensions, and in components installer fallback to extension_administrator.

Moreover path manifest contains complete path to manifest not only filename, therefore the result path was always invalid.

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

• changed the InstallerScriptTrait::getOldManifest function to search in correct path
• added parameters to error message (current and new version)

Testing Instructions

Use any extension using InstallerScriptTrait with disallowed downgrades (that is by default) and try to install an old version over existing newer version.

Actual result BEFORE applying this Pull Request

The extension is installed anyway,

Expected result AFTER applying this Pull Request

The extension is not installed, error message is displayed,

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed