Here are the changes that I found.  Looks like mostly changes to the Adsense.

In admin/skins/app_LocalResources/Banner.ascx.vb the following code was removed:

    <data name="BannerName.Text">
        <value>Google Adsense</value>
    </data>
    <data name="BannerURL.Text">
        <value>http://www.dotnetnukecorp.com/tabid/79/default.aspx</value>
    </data>
    <data name="BannerFile.Text">
        <value>http://www.dotnetnukecorp.com/banner.gif</value>
    </data>
    <data name="BannerScript.Text">
    <value>&lt;script type="text/javascript"&gt;&lt;!--
google_ad_client = "pub-9770992166002654";
google_ad_width = 468;
google_ad_height = 60;
google_ad_format = "468x60_as";
google_ad_type = "text";
google_ad_channel = "";
google_color_border = "000000";
google_color_bg = "FFFFFF";
google_color_link = "0000FF";
google_color_text = "000000";
google_color_url = "008000";
//--&gt;&lt;/script&gt;
&lt;script type="text/javascript"
  src="http://pagead2.googlesyndication.com/pagead/show_ads.js"&gt;
&lt;/script&gt;</value>
    </data>

In admin/skins/Banner.ascx.vb removed the following:

               Dim objBanner As BannerInfo

                ' if no banners found
                If arrBanners.Count = 0 Then
                    Dim strBannerScript As String = Services.Localization.Localization.GetString("BannerScript", Services.Localization.Localization.GetResourceFile(Me, MyFileName))
                    If Request.IsLocal = True Then
                        ' local installations will serve a text Google ad
                        If strBannerScript <> "" Then
                            objBanner = New BannerInfo
                            objBanner.BannerId = -1
                            objBanner.BannerTypeId = 7 ' script
                            objBanner.Description = strBannerScript
                            arrBanners.Add(objBanner)
                        End If
                    Else
                        ' remote installations will serve a default banner to Administrators, inviting them to Adsense enbale their site
                        If PortalSecurity.IsInRole(PortalSettings.AdministratorRoleName) = True Then
                            Dim strBannerName As String = Services.Localization.Localization.GetString("BannerName", Services.Localization.Localization.GetResourceFile(Me, MyFileName))
                            Dim strBannerURL As String = Services.Localization.Localization.GetString("BannerURL", Services.Localization.Localization.GetResourceFile(Me, MyFileName))
                            Dim strBannerFile As String = Services.Localization.Localization.GetString("BannerFile", Services.Localization.Localization.GetResourceFile(Me, MyFileName))
                            If strBannerName <> "" And strBannerURL <> "" And strBannerFile <> "" Then
                                ' add default banner
                                objBanner = New BannerInfo
                                objBanner.BannerId = -1
                                objBanner.BannerTypeId = 1 ' banner
                                objBanner.BannerName = strBannerName
                                objBanner.URL = strBannerURL
                                If strBannerFile.IndexOf("://") = -1 Then
                                    strBannerFile = Common.Globals.ApplicationPath & strBannerFile
                                End If
                                objBanner.ImageFile = strBannerFile
                                arrBanners.Add(objBanner)
                            End If
                        End If
                    End If
                End If

In admin/vendors/DisplayBaners.ascx.vb changed this:

In portals/_default/DotNetNuke.template changed this:

   <banneradvertising>1</banneradvertising>

to this:

 <banneradvertising>0</banneradvertising>

In admin/security/SignIn.ascx.vb the problem with Login Module was fixed.

Changed this:

            'Else
                ' if user is already authenticated then redirect to current page
                Response.Redirect(NavigateURL(), True)

To this:

Else ' user is already authenticated

                ' if a Login Page has not been specified for the portal
                If IsAdminControl() Then
                    ' redirect to current page
                    Response.Redirect(NavigateURL(), True)
                Else ' make module container invisible
                    ContainerControl.Visible = False
                End If

In admin/skins/Logo.ascx.vb change this: 

             hypLogo.NavigateUrl = AddHTTP(GetDomainName(Request)) & "/" & glbDefaultPage & "?base"
to this:
            hypLogo.NavigateUrl = GetPortalDomainName(PortalSettings.PortalAlias.HTTPAlias, Request) & "/" & glbDefaultPage & "?base"

Changed redirect after registration in admin/users/ManageUsers.ascx.vb:

                If CType(setting, Integer) = Null.NullInteger Then
                    If Not Request.QueryString("returnurl") Is Nothing Then
                        ' return to the url passed to register
                        _RedirectURL = HttpUtility.UrlDecode(Request.QueryString("returnurl"))
                    Else
                        ' redirect to current page
                        _RedirectURL = NavigateURL()
                    End If
                Else ' redirect to after registration page
                    _RedirectURL = NavigateURL(CType(setting, Integer))
                End If

The previous were changes to the website files. Following are the changes to the Core Library. 

The only significant change was to the TabPermissionsController where these two lines were removed:

                permissionInfo.RoleID = Convert.ToInt32(Null.SetNull(dr("RoleID"), permissionInfo.RoleID))
                permissionInfo.RoleName = Convert.ToString(Null.SetNull(dr("RoleName"), permissionInfo.RoleName))

One change in the Localization Token replacements to check for Lower Case

And the rest were for the version change from 4.5.2 to 4.5.3