codeql/change-notes/1.20/analysis-csharp.md

Improvements to C# analysis

General improvements

New queries

Query	Tags	Purpose

Changes to existing queries

@name of query (Query ID)	Impact on results	How/why the query has changed
Off-by-one comparison against container length (cs/index-out-of-bounds)	Fewer false positives	Results have been removed when there are additional guards on the index.
Dereferenced variable is always null (cs/dereferenced-value-is-always-null)	Improved results	The query has been rewritten from scratch, and the analysis is now based on static single assignment (SSA) forms. The query is now enabled by default in LGTM.
Dereferenced variable may be null (cs/dereferenced-value-may-be-null)	Improved results	The query has been rewritten from scratch, and the analysis is now based on static single assignment (SSA) forms. The query is now enabled by default in LGTM.
SQL query built from user-controlled sources (cs/sql-injection), Improper control of generation of code (cs/code-injection), Uncontrolled format string (cs/uncontrolled-format-string), Clear text storage of sensitive information (cs/cleartext-storage-of-sensitive-information), Exposure of private information (cs/exposure-of-sensitive-information)	More results	Data sources have been added from user controls in System.Windows.Forms.
Use of default ToString() (cs/call-to-object-tostring)	Fewer false positives	Results have been removed for char arrays passed to StringBuilder.Append(), which were incorrectly marked as using ToString.
Use of default ToString() (cs/call-to-object-tostring)	Fewer results	Results have been removed when the object is an interface or an abstract class.
Unused format argument (cs/format-argument-unused)	Fewer false positives	Results have been removed where the format string is empty. This is often used as a default value and is not an interesting result.
Double-checked lock is not thread-safe (cs/unsafe-double-checked-lock)	Fewer false positives, more true positives	Results have been removed where the underlying field was not updated in the lock statement, or where the field is a struct. Results have been added where there are other statements inside the lock statement.
Using a package with a known vulnerability (cs/use-of-vulnerable-package)	More results	This query detects packages vulnerable to CVE-2019-0657.

Changes to code extraction

• Fix extraction of for statements where the condition declares new variables using is.
• Initializers of stackalloc arrays are now extracted.

Changes to QL libraries

• The class TrivialProperty now includes library properties determined to be trivial using CIL analysis. This may increase the number of results for all queries that use data flow.
• Taint-tracking steps have been added for the Json.NET package. This will improve results for queries that use taint-tracking.
• Support has been added for EntityFrameworkCore, including
  • Stored data flow sources
  • Sinks for SQL expressions
  • Data flow through fields that are mapped to the database.

Changes to the autobuilder