Warning: preg_match(): Compilation failed: nothing to repeat at offset 20

  • For some reason, Wordfence is kicking in on a WordPress installation set up in a subfolder of the main WP install that has Wordfence enabled (the subfolder WP does not have Wordfence installed or enabled), and on every form submission/file upload on the subfolder instance we get about 20-30 entries like this listed on the page as errors:

    Warning: preg_match(): Compilation failed: nothing to repeat at offset 20 in /home/site/public_html/wp-content/plugins/wordfence/vendor/wordfence/wf-waf/src/lib/rules.php on line 728

    What in the world does that mean?

    And how do we fix that?

Viewing 1 replies (of 1 total)

  • Hi @crazyserb,

    This warning is related to the Firewall rule that scans file uploads with the malware signatures.
    It can appear if the rule doesn’t work on your PCRE (Perl Compatible Regular Expressions) version.

    We have a new Wordfence update coming up this week which will fix this type of issue. However, if you’d like to get rid of these warnings immediately you can temporarily disable the Malicious File Upload rule on the Web Application Firewall:

    • Go to the Wordfence Firewall page
    • In Web Application Firewall (default tab), scroll down to the Rules section
    • Uncheck the “file_upload –> Malicious File Upload (Patterns)“ checkbox
Viewing 1 replies (of 1 total)
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