ExpressionEngine 6.0.2 PHP Code Injection

`----------------------------------------------------------------------------  
ExpressionEngine <= 6.0.2 (Translate::save) PHP Code Injection   
Vulnerability  
----------------------------------------------------------------------------  
  
  
[-] Software Link:  
  
https://expressionengine.com/  
  
  
[-] Affected Versions:  
  
Version 6.0.2 and prior versions.  
Version 5.4.1 and prior versions.  
  
  
[-] Vulnerability Description:  
  
The vulnerable code is located in the   
"ExpressionEngine\Controller\Utilities\Translate::save()" method:  
  
362. private function save($language, $file)  
363. {  
364.  
365. $file = ee()->security->sanitize_filename($file);  
366.  
367. $dest_dir = $this->languages_dir . $language . '/';  
368. $filename = $file . '_lang.php';  
369. $dest_loc = $dest_dir . $filename;  
370.  
371. $str = '<?php' . "\n" . '$lang = array(' . "\n\n\n";  
372.  
373. ee()->lang->loadfile($file);  
374.  
375. foreach ($_POST as $key => $val) {  
376. $val = str_replace('<script', '', $val);  
377. $val = str_replace('<iframe', '', $val);  
378. $val = str_replace(array("\\", "'"), array("\\\\",   
"\'"), $val);  
379.  
380. $str .= '\'' . $key . '\' => ' . "\n" . '\'' . $val   
. '\'' . ",\n\n";  
381. }  
382.  
383. $str .= "''=>''\n);\n\n";  
384. $str .= "// End of File";  
  
[...]  
  
400. $this->load->helper('file');  
401.  
402. if (write_file($dest_loc, $str)) {  
403. ee('CP/Alert')->makeInline('shared-form')  
404. ->asSuccess()  
405. ->withTitle(lang('translations_saved'))  
406. ->addToBody(sprintf(lang('file_saved'),   
$dest_loc))  
407. ->defer();  
  
User input passed via keys of POST parameters is not properly sanitized   
before being assigned  
to the "$str" variable at line 380. Such a variable will be used in a   
call to the "write_file()"  
function at line 402, trying to write user supplied content into the  
/system/user/language/[lang]/[file]_lang.php file. This can be exploited   
to inject and execute arbitrary PHP code. Successful exploitation of   
this vulnerability requires an account with  
permissions to access the CP translation system utilities.  
  
  
[-] Solution:  
  
Upgrade to version 6.0.3, 5.4.2, or later.  
  
  
[-] Disclosure Timeline:  
  
[03/02/2021] - Vendor notified through HackerOne  
[15/02/2021] - Vulnerability acknowledged by the vendor  
[16/02/2021] - CVE number assigned  
[17/02/2021] - Version 6.0.3 released  
[04/03/2021] - Version 5.4.2 released  
[15/03/2021] - Public disclosure  
  
  
[-] CVE Reference:  
  
The Common Vulnerabilities and Exposures project (cve.mitre.org)  
has assigned the name CVE-2021-27230 to this vulnerability.  
  
  
[-] Credits:  
  
Vulnerability discovered by Egidio Romano.  
  
  
[-] Other References:  
  
https://hackerone.com/reports/1093444  
  
  
[-] Original Advisory:  
  
http://karmainsecurity.com/KIS-2021-03  
`