Disable Magento extensions by

• Opening the relevant extension file in app/etc/modules
• Set active to false
• Save file back to file system
• Refresh cache

If your backend is broken and you cannot refresh cache you can manually remove from var/cache.

If you’re still having issues with the site after disabling WebShopApps extensions then the problem is caused by some external factor. Refreshing the cache will cause all latest files to be uploaded, so it could be as a result of doing this.