For almost all inputs which are saved to the database, CiviCRM automatically uses `CRM_Utils_API_HTMLInputCoder::encodeInput()` to apply a *partial* encoding for HTML output. This encoding step happens at a low level for inputs passed through the API or the BAO (except for fields noted in `CRM_Utils_API_HTMLInputCoder::getSkipFields()`). So if you're using the API or the BAO to process your input you don't need to do anything special.
If, for some strange reason, you happen to be writing untrusted data to the database directly with SQL, you should encode this data in a fashion consistent with `CRM_Utils_API_HTMLInputCoder::encodeInput()`.
Note that `CRM_Utils_API_HTMLInputCoder::encodeInput()` only encodes `<` and `>`. It does *not* encode quotes. This has some special implications for how you should [encode your HTML outputs](/security/outputs.md#html).
### Input purification {:#input-purification}
When accepting untrusted data with rich text (uncommon), pass the data through `CRM_Utils_String::purifyHTML` to remove XSS.
## `GET` parameters
If you have a page or a form which reads parameters from the URL (aka `GET` parameters) like `?cid=1234` or `?action=add`, it's important to understand that attackers can somewhat easily deceive *privileged users* into submitting malicious `GET` requests by directing the user to an email or website with content like:
...
...
@@ -48,3 +33,17 @@ if (!preg_match(':^[a-zA-Z0-9\-_/]+$:', $angPage)) {
TODO
## When saving to the database
### Input encoding {:#input-encoding}
For almost all inputs which are saved to the database, CiviCRM automatically uses `CRM_Utils_API_HTMLInputCoder::encodeInput()` to apply a *partial* encoding for HTML output. This encoding step happens at a low level for inputs passed through the API or the BAO (except for fields noted in `CRM_Utils_API_HTMLInputCoder::getSkipFields()`). So if you're using the API or the BAO to process your input you don't need to do anything special.
If, for some strange reason, you happen to be writing untrusted data to the database directly with SQL, you should encode this data in a fashion consistent with `CRM_Utils_API_HTMLInputCoder::encodeInput()`.
Note that `CRM_Utils_API_HTMLInputCoder::encodeInput()` only encodes `<` and `>`. It does *not* encode quotes. This has some special implications for how you should [encode your HTML outputs](/security/outputs.md#html).
### Input purification {:#input-purification}
When accepting untrusted data with rich text (uncommon), pass the data through `CRM_Utils_String::purifyHTML` to remove XSS.
