[FEATURE] Security improvements

[pbek]

We want to tackle some security improvements.

#	Severity	File	Issue	Fix Applied
4	HIGH	services/owncloudservice.cpp:991	URL with embedded plaintext password logged via qDebug()	Replaced with a safe log line that omits the password
3	HIGH	services/owncloudservice.cpp:603, widgets/settings/networksettingswidget.cpp:50	ignoreSSLErrors defaulted to true, disabling TLS validation on fresh installs	Changed default to false
13	Low	dialogs/linkdialog.cpp:223, libraries/qmarkdowntextedit/qmarkdowntextedit.cpp:1578	URL scheme completion defaulted to http://	Changed to https://
5	Medium	services/databaseservice.cpp:1061	Table name concatenated directly into SQL query	Added a whitelist of valid table names before concatenation
11	Low	libraries/fakevim/fakevim/fakevimhandler.cpp:903	Qt < 5.15 path passed full command string to proc.start(), enabling shell interpretation	Replaced with manual split + direct process invocation; executable is now validated from the split result
9	Medium	services/mcpservice.cpp:200,217,246	MCP localhost server used Access-Control-Allow-Origin: *	Restricted to http://localhost
7	Medium	utils/gui.cpp:1377	D-Bus query used /bin/sh -c shell invocation	Replaced with direct dbus-send invocation using a proper QStringList arguments; executable looked up via QStandardPaths::findExecutable
12	Low	dialogs/updatedialog.cpp:440	Temp script file had permissions set after writing, and used broader `ExeUser	ReadUser

[pbek]

26.5.1

• Fixed several security issues (for #3591)
  • Fixed a plaintext password leak where a qDebug() call in
    restoreTrashedNoteOnServer() logged a QUrl containing the embedded
    server password
  • Changed the default value of the Ignore SSL errors network setting from
    true to false to prevent man-in-the-middle attacks on fresh installs
  • The MCP server CORS header was narrowed from the wildcard * to
    http://localhost to reduce the DNS-rebinding / localhost attack surface
  • The Linux dark-mode D-Bus check now invokes dbus-send directly instead of
    via /bin/sh -c, eliminating unnecessary shell interpretation
  • URLs typed without a scheme now default to https:// instead of http://
  • A table-name whitelist was added to generateDatabaseTableSha1Signature()
    to guard against SQL injection via concatenated table names
  • The FakeVim shell-filter (!) on Qt < 5.15 no longer passes the full
    command string to QProcess::start() (which invoked the shell); the
    executable is now split out and run directly in all Qt versions
  • The macOS updater temporary script file now has owner-only permissions
    (0700) set before its content is written, hardening against
    TOCTOU replacement by other local users