Androidの在庫ブラウザをダウンロードしてください -- malware フィールド と stock-browser フィールド android 関連 問題

Android 4.4.2 Kitkat Stock Browser
If I start it or open new tab, downloading of apk file (xb_client_blah-blah-blah.apk) from site no.stepfaster.com immediatelly starts instead of opening page which is set as default.
Obviosly some malware fixed Browser's config. Which file and how to fix this?
No root. Browser was stopped and cache cleaned several time. Nothing was installed before this. The mentioned site contains AdSDK apk-files.

I had this today.

I cleared the download manager cache and rebooted, but the problem persisted.

I then re cleared the download manager cache AND the stock browser cache, rebooted and the issue had stopped.

I cleared not only the cache but also the data of the browser. Then I desactivated it.Then I cleared the cache of the application launcher. I tracked down and removed the apk un Download. If you click on them before removing, you can see what the app have access to. I rebooted. I activated Browser again. I rebooted again. Now it works fine. It stopped downloading apk when open. I may ne still infected by the previous apk, though.