{"id":"CVE-2026-91831","kind":"vulnerability","aliases":["CVE-2026-91831"],"related":[],"title":"Subscribe to Comments WordPress plugin: email header injection via sender name","description":"The Subscribe to Comments WordPress plugin before 2.3.3 does not sanitise newline characters from a notification sender-name setting before using it in e-mail headers, allowing users with Author-level access and above to inject arbitrary e-mail headers, such as a hidden Bcc, and to spoof the sender.","summary":"The Subscribe to Comments WordPress plugin before 2.3.3 does not strip newline characters from its notification sender-name setting before placing it in email headers. An author-level user can inject extra headers such as a hidden Bcc or a spoofed sender.","severity":"low","cvss":3.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["package","self-hosted","wordpress","wordpress-plugin"],"not_affected_if":["no-author-level-users","plugin-2.3.3-or-later","plugin-not-installed"],"how_to_check":"- Check the installed plugin version in the WordPress admin Plugins screen or in `wp plugin get subscribe-to-comments --field=version`\n- Confirm whether the plugin is active and whether the sender-name setting is used for notifications","fix":"- Update the Subscribe to Comments plugin to `2.3.3` or later\n- Until updated, restrict Author-level and higher accounts to trusted users only","status":"open","published_at":"2026-10-19T07:16:32+00:00","first_seen_at":"2026-10-23T21:57:17+00:00","triaged_at":"2026-10-25T04:43:18+00:00","updated_at":"2026-10-25T04:43:18+00:00","category":"package","confidence":0.6,"triage":{"at":"2026-10-25T04:43:18Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Subscribe to Comments plugin to `2.3.3` or later\n- Until updated, restrict Author-level and higher accounts to trusted users only","reach":"internet","title":"Subscribe to Comments WordPress plugin: email header injection via sender name","impact":"low","summary":"The Subscribe to Comments WordPress plugin before 2.3.3 does not strip newline characters from its notification sender-name setting before placing it in email headers. An author-level user can inject extra headers such as a hidden Bcc or a spoofed sender.","category":"package","nicknames":[],"who_cares":["wordpress","wordpress-plugin","self-hosted"],"confidence":0.6,"needs_auth":"yes","worst_case":"Authors send spoofed emails with hidden Bcc recipients","analyst_note":"","how_to_check":"- Check the installed plugin version in the WordPress admin Plugins screen or in `wp plugin get subscribe-to-comments --field=version`\n- Confirm whether the plugin is active and whether the sender-name setting is used for notifications","needs_analyst":false,"not_affected_if":["plugin-not-installed","plugin-2.3.3-or-later","no-author-level-users"],"who_is_affected":"Sites running the Subscribe to Comments plugin before 2.3.3 that have users with Author role or above. The exposure depends on those users being able to edit the sender-name setting, so sites with only administrators or no multi-user publishing can deprioritise this. Sites that do not use the plugin can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.000615,"input_tokens":3322,"output_tokens":566,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-91831':14A,17A '2.3.3':33B,77C 'access':104C 'allow':98C 'arbitrari':109C 'author':54B,102C 'author-level':53B,101C 'bcc':65B,118C 'charact':38B,82C 'comment':3A,29B,73C 'cve':12A,15A 'e':95C,111C 'e-mail':94C,110C 'email':6A,50B 'extra':59B 'header':7A,51B,60B,97C,113C 'hidden':64B,117C 'host':21B 'inject':8A,58B,108C 'level':55B,103C 'mail':96C,112C 'name':11A,44B,88C 'newlin':37B,81C 'notif':41B,85C 'packag':18B 'place':47B 'plugin':5A,25B,31B,75C 'sanitis':80C 'self':20B 'self-host':19B 'sender':10A,43B,69B,87C,123C 'sender-nam':42B,86C 'set':45B,89C 'spoof':68B,121C 'strip':36B 'subscrib':1A,27B,71C 'use':91C 'user':56B,99C 'via':9A 'wordpress':4A,22B,24B,30B,74C 'wordpress-plugin':23B","nicknames":[],"mitigations":[],"who_affected":"Sites running the Subscribe to Comments plugin before 2.3.3 that have users with Author role or above. The exposure depends on those users being able to edit the sender-name setting, so sites with only administrators or no multi-user publishing can deprioritise this. Sites that do not use the plugin can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-19T07:16:32+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N","cvss_by":"contact@wpscan.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-91831","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91831","severity":null,"published_at":"2026-10-19T07:16:32+00:00","modified_at":"2026-10-19T21:02:51+00:00","first_seen_at":"2026-10-23T21:57:17+00:00","fetched_at":"2026-10-23T22:28:56+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}