SSRS stored a bunch of different objects in the Catalog table.
SELECT
ModifiedDate
, [Path]
, CASE [Type]
WHEN 2 THEN 'Report'
END AS TypeName
, CAST(CAST(content AS varbinary(max)) AS xml)
, [Description]
FROM ReportServer.dbo.[Catalog]
WHERE
[Type] IN (2)
ORDER BY ModifiedDate DESC
The content CASTs will render as a hyperlink in SSMS; click and you can view the XML.