Tagged template literals and the hack that will never go away

submited by
Style Pass
2022-06-23 12:00:10

Tagged template literals were added to Javascript as part of ES 2015. While a fair bit has been written about them, I’m going to argue their significance is underappreciated and I’m hoping this post will help change that. In part, it’s significant because it strikes at the root of a problem people had otherwise resigned themselves to living with: SQL injection.

Just so we are clear, before ES 2015, combining query strings with untrusted user input to create a SQL injection was done via concatenation using the plus operator.

By itself this addition is really only remarkable for not being included in the language sooner. The backticks are weird, but it gives us some much-needed multiline string support and a very Rubyish string interpolation syntax. It’s pairing this new syntax with another language feature known as tagged templates that has a real potential to make an impact on SQL injections.

What you see above is just a function call, but it no longer works like other languages. Instead of doing the variable interpolation first and then calling the sql function with select * from widgets where id = 1;, the sql function is called with an array of strings and the variables that are supposed to be interpolated.

Leave a Comment