Steps to reproduce:

1. Open <EZROOT>/ezpublish_legacy/extension/ezfind/extension.xml;
2. Look at the following block:

<software>
    <uses>
        <name>Solr</name>
        <license>Apache License, Version 2.0</license>
        <copyright>The Apache Software Foundation.</copyright>
        <info_url>http://lucene.apache.org/solr/</info_url>
        <version>3.5</version>
    </uses>
</software>

"version" reads "3.5", should read "3.6.1", as is specified in the online documentation for eZ Find LS 5.0.0:

"eZ Find uses the open source enterprise search server Solr (3.6.1 version)"

Another way to confirm this is to go to http://localhost:8983/solr/admin/ and then to "INFO". There, you can see the SOLR version being used:

...
Lucene Specification Version: 3.6.1
...