@tnightingale please say thank you to your hosting provider for me:
This is the ModSecurity rule in question. Disabling it gets the pagination links working again.
#
# Some servers rely on the request Accept header to determine what charset to respond with.
# This rule restricts these to familiar charsets.
#
# Regular expression generated from util/regexp-assemble/data/920600.data.
# To update the regular expression run the following shell script
# (consult util/regexp-assemble/README.md for details):
# util/regexp-assemble/regexp-assemble.py update 920600
#
SecRule REQUEST_HEADERS:Accept "!@rx ^(?:(?:\*|[^\"(),\/:;<=>?![\x5c\]{}]+)\/(?:\*|[^\"(),\/:;<=>?![\x5c\]{}]+))(?:\s*+;\s*+(?:(?:charset\s*+=\s*+(?:\"?(?:iso-8859-15?|windows-1252|utf-8)\b\"?))|(?:(?:c(?:h(?:a(?:r(?:s(?:e[^t\"(),\/:;<=>?![\x5c\]{}]|[^e\"(),/:;<=>?![\x5c\]{}])|[^s\"(),/:;<=>?![\x5c\]{}])|[^r\"(),/:;<=>?![\x5c\]{}])|[^a\"(),/:;<=>?![\x5c\]{}])|[^h\"(),/:;<=>?![\x5c\]{}])|[^c\"(),/:;<=>?![\x5c\]{}])[^\"(),/:;<=>?![\x5c\]{}]*(?:)\s*+=\s*+[^(),/:;<=>?![\x5c\]{}]+)|;?))*(?:\s*+,\s*+(?:(?:\*|[^\"(),\/:;<=>?![\x5c\]{}]+)\/(?:\*|[^\"(),\/:;<=>?![\x5c\]{}]+))(?:\s*+;\s*+(?:(?:charset\s*+=\s*+(?:\"?(?:iso-8859-15?|windows-1252|utf-8)\b\"?))|(?:(?:c(?:h(?:a(?:r(?:s(?:e[^t\"(),\/:;<=>?![\x5c\]{}]|[^e\"(),/:;<=>?![\x5c\]{}])|[^s\"(),/:;<=>?![\x5c\]{}])|[^r\"(),/:;<=>?![\x5c\]{}])|[^a\"(),/:;<=>?![\x5c\]{}])|[^h\"(),/:;<=>?![\x5c\]{}])|[^c\"(),/:;<=>?![\x5c\]{}])[^\"(),/:;<=>?![\x5c\]{}]*(?:)\s*+=\s*+[^(),/:;<=>?![\x5c\]{}]+)|;?))*)*$" \
"id:920600,\
phase:1,\
block,\
t:none,t:lowercase,\
msg:'Illegal Accept header: charset parameter',\
logdata:'%{MATCHED_VAR}',\
tag:'application-multi',\
tag:'language-multi',\
tag:'platform-multi',\
tag:'attack-protocol',\
tag:'paranoia-level/1',\
tag:'OWASP_CRS',\
ver:'OWASP_CRS/3.3.4',\
severity:'CRITICAL',\
setvar:'tx.anomaly_score_pl1=+%{tx.critical_anomaly_score}'"
Obviously I’d still like to see Events Calendar fix this. It’s a default rule in one of—if not *the*—the most commonly used WAF packages.
