Escape double quotes in sp_LogHunter @custom_message

The #search.command computed column builds an xp_readerrorlog call
with the search string wrapped in double quotes:

  EXECUTE master.dbo.xp_readerrorlog [log], 1, "<search>", " ", ...

@custom_message is concatenated straight into the "<search>" slot
without escaping, so a literal " in the user-supplied message closes
the first argument early. The rest of the @custom_message gets parsed
as T-SQL and sp_executesql raises "Incorrect syntax near '+'" or a
similar message. Verified by calling with @custom_message = N'hello"+injection'.

Doubled the quote on the way in: REPLACE(@custom_message, N'"', N'""').
xp_readerrorlog accepts the doubled quote as a literal inside the
search string. Normal strings (no quotes) behave the same as before.
Verified against the QsCleanupTest disk-full message lookup with
@custom_message = N'Microsoft'.

Note: this is not a privilege-escalation vector — xp_readerrorlog
already requires securityadmin-level access — but cryptic syntax
errors from a valid-looking input are a real operator footgun.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: erikdarlingdata

sp_LogHunter/sp_LogHunter.sql

@@ -491,7 +491,13 @@ BEGIN
     (
         VALUES
            (
-                N'"' + @custom_message + '"',
+                /* xp_readerrorlog search strings are wrapped in double quotes
+                   (see the #search.command computed column), so any literal "
+                   inside the user-supplied @custom_message must be doubled to
+                   avoid closing the argument early and producing an
+                   "Incorrect syntax near '+'" error when sp_executesql parses
+                   the generated batch. */
+                N'"' + REPLACE(@custom_message, N'"', N'""') + N'"',
                 N'"' + CONVERT(nvarchar(10), DATEADD(DAY, @days_back, SYSDATETIME()), 112) + N'"',
                 N'"' + CONVERT(nvarchar(30), @start_date) + N'"',
                 N'"' + CONVERT(nvarchar(30), @end_date) + N'"'