{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/cve-2026-4883/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[{"cvss":9.8,"id":"CVE-2026-4883"}],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Piotnet Forms plugin \u003c= 2.1.40"],"_cs_severities":["critical"],"_cs_tags":["arbitrary-file-upload","wordpress","plugin","CVE-2026-4883"],"_cs_type":"advisory","_cs_vendors":["WordPress"],"content_html":"\u003cp\u003eThe Piotnet Forms plugin for WordPress is vulnerable to arbitrary file upload due to insufficient file type validation in the \u0026lsquo;piotnetforms_ajax_form_builder\u0026rsquo; function. This vulnerability affects all versions up to and including 2.1.40. The plugin employs an inadequate extension blacklist, blocking only extensions like .php, .phpt, .php5, .php7, and .exe, but failing to prevent uploads of potentially dangerous extensions like .phar or .phtml. An unauthenticated attacker can exploit this vulnerability to upload arbitrary files to the affected WordPress site\u0026rsquo;s server, which can lead to remote code execution. The vulnerability is only exploitable if a file upload field is present in a form.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eUnauthenticated attacker accesses a WordPress page containing a Piotnet Form with a file upload field.\u003c/li\u003e\n\u003cli\u003eAttacker crafts a malicious file (e.g., a .phar or .phtml file) containing malicious code.\u003c/li\u003e\n\u003cli\u003eAttacker submits the form, uploading the malicious file through the \u0026lsquo;piotnetforms_ajax_form_builder\u0026rsquo; function.\u003c/li\u003e\n\u003cli\u003eThe plugin\u0026rsquo;s insufficient file type validation allows the file to be uploaded to the server.\u003c/li\u003e\n\u003cli\u003eThe attacker determines the upload path of the malicious file.\u003c/li\u003e\n\u003cli\u003eAttacker accesses the uploaded malicious file via a web browser request.\u003c/li\u003e\n\u003cli\u003eThe web server executes the malicious code contained in the uploaded file (e.g., .phar or .phtml).\u003c/li\u003e\n\u003cli\u003eAttacker achieves remote code execution on the WordPress server.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of this vulnerability allows unauthenticated attackers to upload arbitrary files, potentially leading to remote code execution on the affected WordPress server. This can result in complete compromise of the website, including data theft, defacement, or further malicious activities. The CVSS v3.1 base score for this vulnerability is 9.8, indicating a critical severity.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade the Piotnet Forms plugin to a version beyond 2.1.40 to patch CVE-2026-4883.\u003c/li\u003e\n\u003cli\u003eImplement a web server rule to block execution of PHP code from the /wp-content/uploads/piotnetforms/ directory to prevent uploaded files from being executed.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule detecting uploads of files with dangerous extensions to the /wp-content/uploads/piotnetforms/ directory to identify potential exploitation attempts.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-05-19T13:17:33Z","date_published":"2026-05-19T13:17:33Z","id":"https://feed.craftedsignal.io/briefs/2026-05-piotnet-forms-file-upload/","summary":"The Piotnet Forms plugin for WordPress is vulnerable to arbitrary file upload due to missing file type validation in the 'piotnetforms_ajax_form_builder' function, allowing unauthenticated attackers to upload arbitrary files and potentially achieve remote code execution.","title":"Piotnet Forms WordPress Plugin Arbitrary File Upload Vulnerability (CVE-2026-4883)","url":"https://feed.craftedsignal.io/briefs/2026-05-piotnet-forms-file-upload/"}],"language":"en","title":"CraftedSignal Threat Feed — CVE-2026-4883","version":"https://jsonfeed.org/version/1.1"}