SQLi in Relevanssi might allow an admin to read contents of database


Last revised:

If logged in as an administrator on any site, you can go to Settings > Relevanssi Premium and potentially extract all values in the database including password hashes and user activation tokens.

This is achieved by a SQL injection based on the fact that some of the configuration options are appended into a SQL query in a unsafe way.

The configuration page contains the following code, that allows the user to set the option relevanssi_post_type_weights to any value:

function update_relevanssi_options() {
    foreach ($_REQUEST as $key => $value) {
        if (substr($key, 0, strlen('relevanssi_weight_')) == 'relevanssi_weight_') {
            $type = substr($key, strlen('relevanssi_weight_'));
            $post_type_weights[$type] = $value;
    if (count($post_type_weights) > 0) {
        update_option('relevanssi_post_type_weights', $post_type_weights);

Now when a search is made, the function relevanssi_search is called, this appends the user controled value into the SQL query:

$post_type_weights = get_option('relevanssi_post_type_weights');


!empty($post_type_weights['post_tag']) ? $tag = $post_type_weights['post_tag'] : $tag = $relevanssi_variables['post_type_weight_defaults']['post_tag'];

!empty($post_type_weights['category']) ? $cat = $post_type_weights['category'] : $cat = $relevanssi_variables['post_type_weight_defaults']['category'];

$query = "SELECT relevanssi.*, relevanssi.title * $title_boost +
          relevanssi.content + relevanssi.comment * $comment_boost +
          relevanssi.tag * $tag + * $link_boost +
 + relevanssi.category * $cat + relevanssi.excerpt +
          relevanssi.taxonomy + relevanssi.customfield + relevanssi.mysqlcolumn AS tf
          FROM $relevanssi_table AS relevanssi $query_join
          WHERE $term_cond $query_restrictions";

Current state: Fixed

CVSS Summary

CVSS base scores for this vulnerability
Score 8.5 High
Vector Network
Complexity Low
Authentication Single
Confidentiality Complete
Integrity Complete
Availability None
You can read more about CVSS base scores on Wikipedia or in the CVSS specification.

Proof of concept

  1. Visit /wp-admin/options-general.php?page=relevanssi%2Frelevanssi.php
  2. Assign 0.75' (the default value plus a single quote at the end) to “Tag weight”
  3. Press “Save the options”
  4. Visit /?s=test
  5. The logs should contain the following error because of the syntax error we introduced: “WordPress database error You have an error in your SQL syntax”

Note: while it’s possible to inject syntax errors, it’s currently unknown whether this bug can be used to inject anything that would be useful to an attacker.

Advisory timeline

  • 2017-10-02: Discovered
  • 2017-10-02: Reported to vendor via email
  • 2017-10-03: First response from vendor
  • 2017-10-03: Version 3.6.1 released which contains a fix for this bug
  • 2018-04-10: Advisory published

Mitigation/further actions

Upgrade to version 3.6.1 or later.