{"id":"CVE-2026-126498","kind":"vulnerability","aliases":["CVE-2026-126498"],"related":[],"title":"WriteFreely: stored XSS via post slug runs script for readers","description":"WriteFreely before 0.17.3 contains a stored cross-site scripting vulnerability that allows authenticated authors to inject HTML by supplying a malicious post slug via the CreatePost API. The raw slug is concatenated into an anchor by augmentReadingDestination() for paid-shortcode posts, executing script for RSS/Atom feed readers, newsletter recipients and ActivityPub viewers.","summary":"WriteFreely before 0.17.3 lets an authenticated author inject HTML through a malicious post slug sent to the CreatePost API. The raw slug is placed into a link for paid-shortcode posts, so script runs for RSS and Atom feed readers, newsletter recipients and ActivityPub viewers.","severity":"medium","cvss":5.4,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"WriteFreely","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["activitypub","other","rss","self-hosted","writefreely"],"not_affected_if":["no-untrusted-authors","version-0.17.3-or-later"],"how_to_check":"- Check the installed WriteFreely version; affected if it is below `0.17.3`.\n- Review posts that use the paid shortcode for unusual slugs containing HTML or script.","fix":"- WriteFreely: move to `0.17.3` or later.","status":"open","published_at":"2026-11-11T01:17:14+00:00","first_seen_at":"2026-11-11T01:24:34+00:00","triaged_at":"2026-11-11T01:25:54+00:00","updated_at":"2026-11-11T01:25:54+00:00","category":"other","confidence":0.7,"triage":{"at":"2026-11-11T01:25:54Z","model":"claude-haiku-5-5","output":{"fix":"- WriteFreely: move to `0.17.3` or later.","reach":"internet","title":"WriteFreely: stored XSS via post slug runs script for readers","impact":"medium","summary":"WriteFreely before 0.17.3 lets an authenticated author inject HTML through a malicious post slug sent to the CreatePost API. The raw slug is placed into a link for paid-shortcode posts, so script runs for RSS and Atom feed readers, newsletter recipients and ActivityPub viewers.","audience":"businesses","category":"other","nicknames":[],"who_cares":["writefreely","self-hosted","rss","activitypub"],"confidence":0.7,"fix_status":"available","needs_auth":"yes","worst_case":"Script runs in readers' browsers and feed or ActivityPub viewers","analyst_note":"","how_to_check":"- Check the installed WriteFreely version; affected if it is below `0.17.3`.\n- Review posts that use the paid shortcode for unusual slugs containing HTML or script.","plain_action":"","product_name":"WriteFreely","needs_analyst":false,"not_affected_if":["version-0.17.3-or-later","no-untrusted-authors"],"who_is_affected":"Self-hosted WriteFreely instances before 0.17.3 where authors can create posts and paid-shortcode posts are used, since the payload reaches readers through feeds, newsletters and ActivityPub. Instances that have only trusted authors or no paid-shortcode posts are at lower risk, but upgrading removes the issue.","user_interaction":"yes","product_ecosystem":"vendor","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000759,"input_tokens":4661,"output_tokens":586,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-126498':13A,16A '-2026':12A,15A '0.17.3':27B,73C 'activitypub':18B,69B,123C 'allow':83C 'anchor':106C 'api':43B,98C 'atom':63B 'augmentreadingdestin':108C 'authent':30B,84C 'author':31B,85C 'concaten':103C 'contain':74C 'createpost':42B,97C 'cross':78C 'cross-sit':77C 'cve':11A,14A 'execut':114C 'feed':64B,118C 'host':23B 'html':33B,88C 'inject':32B,87C 'let':28B 'link':51B 'malici':36B,92C 'newslett':66B,120C 'paid':54B,111C 'paid-shortcod':53B,110C 'place':48B 'post':5A,37B,56B,93C,113C 'raw':45B,100C 'reader':10A,65B,119C 'recipi':67B,121C 'rss':20B,61B 'rss/atom':117C 'run':7A,59B 'script':8A,58B,80C,115C 'self':22B 'self-host':21B 'sent':39B 'shortcod':55B,112C 'site':79C 'slug':6A,38B,46B,94C,101C 'store':2A,76C 'suppli':90C 'via':4A,95C 'viewer':70B,124C 'vulner':81C 'writefre':1A,24B,25B,71C 'writefreely':17A 'xss':3A","nicknames":[],"mitigations":[],"who_affected":"Self-hosted WriteFreely instances before 0.17.3 where authors can create posts and paid-shortcode posts are used, since the payload reaches readers through feeds, newsletters and ActivityPub. Instances that have only trusted authors or no paid-shortcode posts are at lower risk, but upgrading removes the issue.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":["writefreely"],"ptokens":["writefreely"],"labels":["activitypub","medium","other","rss","selfhosted","vendor","writefreely"],"campaign_type":null,"search_a":"'-126498':13A,16A '-2026':12A,15A 'cve':11A,14A 'post':5A 'reader':10A 'run':7A 'script':8A 'slug':6A 'store':2A 'via':4A 'writefre':1A 'writefreely':17A 'xss':3A","search_b":"'0.17.3':27B 'activitypub':18B,69B 'api':43B 'atom':63B 'authent':30B 'author':31B 'createpost':42B 'feed':64B 'host':23B 'html':33B 'inject':32B 'let':28B 'link':51B 'malici':36B 'newslett':66B 'paid':54B 'paid-shortcod':53B 'place':48B 'post':37B,56B 'raw':45B 'reader':65B 'recipi':67B 'rss':20B,61B 'run':59B 'script':58B 'self':22B 'self-host':21B 'sent':39B 'shortcod':55B 'slug':38B,46B 'viewer':70B 'writefre':24B,25B","search_c":"'0.17.3':73C 'activitypub':123C 'allow':83C 'anchor':106C 'api':98C 'augmentreadingdestin':108C 'authent':84C 'author':85C 'concaten':103C 'contain':74C 'createpost':97C 'cross':78C 'cross-sit':77C 'execut':114C 'feed':118C 'html':88C 'inject':87C 'malici':92C 'newslett':120C 'paid':111C 'paid-shortcod':110C 'post':93C,113C 'raw':100C 'reader':119C 'recipi':121C 'rss/atom':117C 'script':80C,115C 'shortcod':112C 'site':79C 'slug':94C,101C 'store':76C 'suppli':90C 'via':95C 'viewer':124C 'vulner':81C 'writefre':71C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-09T22:46:22+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-126498","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-126498","severity":null,"published_at":"2026-11-11T01:17:14+00:00","modified_at":"2026-11-11T01:17:14+00:00","first_seen_at":"2026-11-11T01:24:34+00:00","fetched_at":"2026-11-11T01:24:34+00:00","note":null}],"documents":[{"id":121279,"url":"https://github.com/writefreely/writefreely/commit/d7231d81a914f1314a218d5e8fde6e0341391ccd","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":121280,"url":"https://github.com/writefreely/writefreely/releases/tag/v0.17.3","title":"Release notes: github.com","kind":"release","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Release notes: github.com"},{"id":121281,"url":"https://github.com/writefreely/writefreely/security/advisories/GHSA-cwxm-8ch5-j2vh","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-11-09T22:46:22+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":121282,"url":"https://www.vulncheck.com/advisories/writefreely-before-0.17.3-stored-xss-via-unsanitized-post-slug","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}